I don't understand your problem in depth. Under 1. you write something about collisions. Where do you need to detect collision in a rubiks cube game?

Under 2. you wrote you had set all cubes position to their very center. That is an easy case as you just have to rotate their position and angle vectors. This can be done by using the vec_rotate function.

Could you please describe in more detail what your exact problem is? Please write what you did, what part of your code works and which part does not what you expect it to do. It always of great help to post a screenshot of what you have done and the code you're using. If you think you can describe the problem better in german, just do that. There are a lot of experienced german speaking users on this forum.