diff --git a/forum/api/__init__.py b/forum/api/__init__.py
index 55a7c4a3..f011f620 100644
--- a/forum/api/__init__.py
+++ b/forum/api/__init__.py
@@ -7,6 +7,7 @@
     create_child_comment,
     create_parent_comment,
     delete_comment,
+    get_course_id_by_comment,
     get_parent_comment,
     update_comment,
 )
@@ -25,6 +26,7 @@
 from .threads import (
     create_thread,
     delete_thread,
+    get_course_id_by_thread,
     get_thread,
     get_user_threads,
     update_thread,
@@ -59,6 +61,8 @@
     "delete_thread",
     "delete_thread_vote",
     "get_commentables_stats",
+    "get_course_id_by_comment",
+    "get_course_id_by_thread",
     "get_parent_comment",
     "get_thread",
     "get_thread_subscriptions",
diff --git a/forum/api/comments.py b/forum/api/comments.py
index 63344382..e2440577 100644
--- a/forum/api/comments.py
+++ b/forum/api/comments.py
@@ -11,6 +11,7 @@
 from forum.backends.mongodb.api import (
     create_comment,
     delete_comment_by_id,
+    get_course_id_by_comment_id,
     get_thread_by_id,
     get_thread_id_by_comment_id,
     get_user_by_id,
@@ -21,6 +22,7 @@
 )
 from forum.backends.mongodb.comments import Comment
 from forum.backends.mongodb.threads import CommentThread
+from forum.backends.mongodb import api
 from forum.serializers.comment import CommentSerializer
 from forum.utils import ForumV2RequestError
 
@@ -294,3 +296,15 @@ def create_parent_comment(
         )
     except ValidationError as error:
         raise error
+
+
+def get_course_id_by_comment(comment_id: str) -> str | None:
+    """
+    Return course_id for the matching comment.
+    It searches for comment_id both in mongodb and mysql.
+    """
+    return (
+        get_course_id_by_comment_id(comment_id)
+        or api.get_course_id_by_comment_id(comment_id)
+        or None
+    )
diff --git a/forum/api/search.py b/forum/api/search.py
index e09d887b..789dbd92 100644
--- a/forum/api/search.py
+++ b/forum/api/search.py
@@ -14,8 +14,7 @@ def _get_thread_ids_from_indexes(
     context: str,
     group_ids: list[int],
     text: str,
-    commentable_id: Optional[str] = None,
-    commentable_ids: Optional[str] = None,
+    commentable_ids: Optional[list[str]] = None,
     course_id: Optional[str] = None,
 ) -> tuple[list[str], Optional[str]]:
     """
@@ -39,7 +38,6 @@ def _get_thread_ids_from_indexes(
         context,
         group_ids,
         text,
-        commentable_id=commentable_id,
         commentable_ids=commentable_ids,
         course_id=course_id,
     )
@@ -50,7 +48,6 @@ def _get_thread_ids_from_indexes(
                 context,
                 group_ids,
                 corrected_text,
-                commentable_id=commentable_id,
                 commentable_ids=commentable_ids,
                 course_id=course_id,
             )
@@ -62,28 +59,30 @@ def _get_thread_ids_from_indexes(
 
 def search_threads(
     text: str,
-    sort_key: str,
-    context: str,
     user_id: str,
     course_id: str,
-    group_ids: list[int],
-    author_id: str,
-    thread_type: str,
-    flagged: bool,
-    unread: bool,
-    unanswered: bool,
-    unresponded: bool,
-    count_flagged: bool,
-    commentable_id: str,
-    commentable_ids: str,
+    group_ids: Optional[list[int]] = None,
+    commentable_ids: Optional[list[str]] = None,
+    author_id: Optional[str] = None,
+    thread_type: Optional[str] = None,
+    sort_key: str = "date",
+    context: str = "course",
+    flagged: bool = False,
+    unread: bool = False,
+    unanswered: bool = False,
+    unresponded: bool = False,
+    count_flagged: bool = False,
     page: int = FORUM_DEFAULT_PAGE,
     per_page: int = FORUM_DEFAULT_PER_PAGE,
 ) -> dict[str, Any]:
     """
     Search for threads based on the provided data.
     """
+    group_ids = group_ids or []
+    commentable_ids = commentable_ids or []
+
     thread_ids, corrected_text = _get_thread_ids_from_indexes(
-        context, group_ids, text, commentable_id, commentable_ids, course_id
+        context, group_ids, text, commentable_ids, course_id
     )
 
     data = handle_threads_query(
diff --git a/forum/api/threads.py b/forum/api/threads.py
index 4a1fd680..cf070913 100644
--- a/forum/api/threads.py
+++ b/forum/api/threads.py
@@ -11,6 +11,7 @@
 from forum.backends.mongodb.api import (
     delete_comments_of_a_thread,
     delete_subscriptions_of_a_thread,
+    get_course_id_by_thread_id,
     get_threads,
 )
 from forum.backends.mongodb.api import mark_as_read as mark_thread_as_read
@@ -21,6 +22,7 @@
 )
 from forum.backends.mongodb.threads import CommentThread
 from forum.backends.mongodb.users import Users
+from forum.backends.mysql import api
 from forum.serializers.thread import ThreadSerializer
 from forum.utils import ForumV2RequestError, get_int_value_from_collection, str_to_bool
 
@@ -42,6 +44,7 @@ def _get_thread_data_from_request_data(data: dict[str, Any]) -> dict[str, Any]:
         "close_reason_code",
         "endorsed",
         "pinned",
+        "group_id",
     ]
     result = {field: data.get(field) for field in fields if data.get(field) is not None}
 
@@ -282,6 +285,7 @@ def create_thread(
     anonymous_to_peers: bool = False,
     commentable_id: str = "course",
     thread_type: str = "discussion",
+    group_id: Optional[int] = None,
 ) -> dict[str, Any]:
     """
     Create a new thread.
@@ -295,6 +299,7 @@ def create_thread(
         closed: Whether the thread is closed.
         commentable_id: The ID of the commentable.
         user_id: The ID of the user.
+        group_id: The ID of the group.
     Response:
         The details of the thread that is created.
     """
@@ -307,6 +312,7 @@ def create_thread(
         "anonymous_to_peers": anonymous_to_peers,
         "commentable_id": commentable_id,
         "thread_type": thread_type,
+        "group_id": group_id,
     }
     thread_data: dict[str, Any] = _get_thread_data_from_request_data(data)
 
@@ -376,3 +382,15 @@ def get_user_threads(
     threads = get_threads(params, ThreadSerializer, thread_ids, user_id or "")
 
     return threads
+
+
+def get_course_id_by_thread(thread_id: str) -> str | None:
+    """
+    Return course_id for the matching thread.
+    It searches for thread_id both in mongodb and mysql.
+    """
+    return (
+        get_course_id_by_thread_id(thread_id)
+        or api.get_course_id_by_thread_id(thread_id)
+        or None
+    )
diff --git a/forum/backends/mongodb/api.py b/forum/backends/mongodb/api.py
index 90d6b7c2..a978b454 100644
--- a/forum/backends/mongodb/api.py
+++ b/forum/backends/mongodb/api.py
@@ -975,6 +975,7 @@ def user_to_hash(
     hash_data = {}
     hash_data["username"] = user["username"]
     hash_data["external_id"] = user["external_id"]
+    hash_data["id"] = user["external_id"]
 
     comment_model = Comment()
     thread_model = CommentThread()
@@ -1410,3 +1411,23 @@ def get_thread_id_by_comment_id(parent_comment_id: str) -> str:
     if parent_comment:
         return parent_comment["comment_thread_id"]
     raise ValueError("Comment doesn't have the thread.")
+
+
+def get_course_id_by_thread_id(thread_id: str) -> str | None:
+    """
+    Return course_id for the matching thread.
+    """
+    thread = CommentThread().get(thread_id)
+    if thread:
+        return thread.get("course_id")
+    return None
+
+
+def get_course_id_by_comment_id(comment_id: str) -> str | None:
+    """
+    Return course_id for the matching comment.
+    """
+    comment = Comment().get(comment_id)
+    if comment:
+        return comment.get("course_id")
+    return None
diff --git a/forum/backends/mysql/api.py b/forum/backends/mysql/api.py
index 3f7e52a8..dd52037e 100644
--- a/forum/backends/mysql/api.py
+++ b/forum/backends/mysql/api.py
@@ -1113,3 +1113,23 @@ def find_or_create_user(user_id: str) -> str:
     """Find or create user."""
     user, _ = ForumUser.objects.get_or_create(user__pk=user_id)
     return user.pk
+
+
+def get_course_id_by_thread_id(thread_id: str) -> str | None:
+    """
+    Return course_id for the matching thread.
+    """
+    thread = CommentThread.objects.filter(id=thread_id).first()
+    if thread:
+        return thread.course_id
+    return None
+
+
+def get_course_id_by_comment_id(comment_id: str) -> str | None:
+    """
+    Return course_id for the matching comment.
+    """
+    comment = Comment.objects.filter(id=comment_id).first()
+    if comment:
+        return comment.course_id
+    return None
diff --git a/forum/search/comment_search.py b/forum/search/comment_search.py
index 1d9ff752..e4013580 100644
--- a/forum/search/comment_search.py
+++ b/forum/search/comment_search.py
@@ -93,19 +93,19 @@ class ThreadSearch(CommentSearch):
     def build_must_clause(
         self,
         search_text: str,
-        commentable_id: Optional[str] = None,
-        commentable_ids: Optional[str] = None,
+        commentable_ids: Optional[list[str]] = None,
         course_id: Optional[str] = None,
     ) -> list[dict[str, Any]]:
         """
         Build the 'must' clause for thread-specific Elasticsearch queries based on input parameters.
         """
         must: list[dict[str, Any]] = []
+        commentable_ids = commentable_ids or []
 
-        if commentable_id:
-            must.append({"term": {"commentable_id": commentable_id}})
-        if commentable_ids:
-            must.append({"terms": {"commentable_id": commentable_ids.split(",")}})
+        if len(commentable_ids) == 1:
+            must.append({"term": {"commentable_id": commentable_ids[0]}})
+        elif len(commentable_ids) > 1:
+            must.append({"terms": {"commentable_id": commentable_ids}})
         if course_id:
             must.append({"term": {"course_id": course_id}})
 
@@ -162,15 +162,14 @@ def get_thread_ids(
         group_ids: list[int],
         search_text: str,
         sort_criteria: Optional[list[dict[str, str]]] = None,
-        commentable_id: Optional[str] = None,
-        commentable_ids: Optional[str] = None,
+        commentable_ids: Optional[list[str]] = None,
         course_id: Optional[str] = None,
     ) -> list[str]:
         """
         Retrieve thread IDs based on search criteria.
         """
         must_clause: list[dict[str, Any]] = self.build_must_clause(
-            search_text, commentable_id, commentable_ids, course_id
+            search_text, commentable_ids, course_id
         )
         filter_clause: list[dict[str, Any]] = self.build_filter_clause(
             context, group_ids
@@ -200,8 +199,7 @@ def get_thread_ids_with_corrected_text(
         group_ids: list[int],
         search_text: str,
         sort_criteria: Optional[list[dict[str, str]]] = None,
-        commentable_id: Optional[str] = None,
-        commentable_ids: Optional[str] = None,
+        commentable_ids: Optional[list[str]] = None,
         course_id: Optional[str] = None,
     ) -> list[str]:
         """
@@ -214,7 +212,6 @@ def get_thread_ids_with_corrected_text(
             group_ids,
             search_text,
             sort_criteria,
-            commentable_id,
             commentable_ids,
             course_id,
         )
diff --git a/forum/serializers/thread.py b/forum/serializers/thread.py
index 22e60a59..38db25d7 100644
--- a/forum/serializers/thread.py
+++ b/forum/serializers/thread.py
@@ -94,6 +94,9 @@ def __init__(self, *args: Any, **kwargs: Any) -> None:
         self.count_flagged = self.context_data.pop("count_flagged", False)
         self.include_endorsed = self.context_data.pop("include_endorsed", False)
         self.include_read_state = self.context_data.pop("include_read_state", False)
+        self.merge_question_type_responses = self.context_data.pop(
+            "merge_question_type_responses", False
+        )
 
         # Customize fields based on context
         if not self.with_responses:
@@ -270,6 +273,7 @@ def to_representation(self, instance: dict[str, Any]) -> dict[str, Any]:
                 or self.context_data.get("recursive") is True
             )
             and data.get("thread_type") == "question"
+            and not self.merge_question_type_responses
         ):
             children = data.pop("children")
             data["non_endorsed_responses"] = []
diff --git a/forum/utils.py b/forum/utils.py
index 0b613b74..98d05ca4 100644
--- a/forum/utils.py
+++ b/forum/utils.py
@@ -184,6 +184,35 @@ def get_group_ids_from_params(params: dict[str, Any]) -> list[int]:
     return group_ids
 
 
+def get_commentable_ids_from_params(params: dict[str, Any]) -> list[str]:
+    """
+    Extract commentable IDs from the provided parameters.
+
+    Args:
+        params (dict): A dictionary containing the parameters.
+
+    Returns:
+        list: A list of commentable IDs.
+
+    Raises:
+        ValueError: If both `commentable_id` and `commentable_ids` are specified in the parameters.
+    """
+    if "commentable_id" in params and "commentable_ids" in params:
+        raise ValueError("Cannot specify both commentable_id and commentable_ids")
+
+    commentable_id = params.get("commentable_id")
+    if commentable_id:
+        return [commentable_id]
+
+    commentable_ids = params.get("commentable_ids", [])
+    if isinstance(commentable_ids, str):
+        return commentable_ids.split(",")
+    elif isinstance(commentable_ids, list):
+        return commentable_ids
+
+    return []
+
+
 def get_sort_criteria(sort_key: str) -> Sequence[tuple[str, int]]:
     """
     Generate sorting criteria based on the provided key.
diff --git a/forum/views/search.py b/forum/views/search.py
index 48f16b47..785ac6bf 100644
--- a/forum/views/search.py
+++ b/forum/views/search.py
@@ -12,7 +12,7 @@
 
 from forum.api.search import search_threads
 from forum.constants import FORUM_DEFAULT_PAGE, FORUM_DEFAULT_PER_PAGE
-from forum.utils import get_group_ids_from_params
+from forum.utils import get_commentable_ids_from_params, get_group_ids_from_params
 
 
 class SearchThreadsView(APIView):
@@ -74,8 +74,7 @@ def _validate_and_extract_params(self, request: Request) -> dict[str, Any]:
         # Group IDs extraction
         params["group_ids"] = get_group_ids_from_params(data)
 
-        params["commentable_id"] = data.get("commentable_id")
-        params["commentable_ids"] = data.get("commentable_ids")
+        params["commentable_ids"] = get_commentable_ids_from_params(data)
 
         return params