This is a game engine I developed when I was in year 11 at secondary school. I distinctly remember being able to view and rotate 3D models in the engine that had been exported in a custom binary format. I used DirectX 11 as the rendering library.
Dynamic lighting was implemented that would change as the model was rotated on the screen.
I created an export script for Blender 3D that has been lost. This allowed me to develop models in Blender that could then be exported for use in the game engine.