Is it possible to make pre-rendered (as in AVI or another video format) cutscenes in Unity Free, i.e. displaying it (making it is an easy part at least for me)? How to do it?
Nope. That would be a job for a 3d modeling and animation program. (Blender, Maya, etc)
If i got the question right you have an avi / mpg (or want to make one) and just want to display it in game?
Well, in Unity free it’s not possible unless you find an efficient way to read, parse, decode the images fast enough without the use of external plugins (which are pro only).
If you have Unity pro you can use a MovieTexture or try to use a nativecode plugin.
Displaying/decoding a video is a quite heavy and complex task. In Unity free you’re restricted to pure managed code libraries which have no external dependencies. Most libraries just wrap a native code library that’s provided by the OS, however that can’t be used in the free version of Unity.