Can I mix 2d and 3d scenes in game
I am totally new to Unity and I looked some tutorials and I want to make game which has 3 scenes which are 2d and 2 scenes which are 2d. Is this possible to do or I have to treat all as 3d scenes ? ( I read some books but didn't find or notice solution to this).
Answer
There is only one type of scene in Unity3d, which is fundamentally a 3d scene.
You can however put the Scene View into '2d Mode', this helps when working with 2d content. Here's a good introduction video on the 2d Scene View Mode:
http://unity3d.com/learn/tutorials/modules/beginner/2d/2d-mode
In reality you can mix and match 2d and 3d within one scene or just have a scene display all it's contents as 2d or 3d. This is down to how you have your camera(s) set-up, using Orthographic Projection on the camera to display as 2d - quite often you'll find that a lot of games have at least two cameras set-up in a scene, one camera for displaying the 3d content and a second (Orthographic) camera for displaying the 2d UI.