Are there any limitations on the number of agents or tickets?
No. There are no any limitations.
When I assign a task to someone do they get an email notifying them that they have a task assigned to them?
Yes, you need to configure Notifications for the user:
I've fetched emails from my mailbox, but older emails were not fetched. How can I fetch the entire inbox messages?
Manage --> System --> Tools and fetch all undread emails.
Is it possible to forward customer's email to FreeScout and make it look like it came from the customer?
You can forward email to FreeScout and use "New Conversation" button in the message's dropdown menu:
What do we need to make a complete backup?
You need to backup Database and