im having this issue as well. I think what the OP was trying to ask is how do you back completely out of a game so that its no longer running in the background. If you hit the windows button it takes you to the home screen, but hitting back takes you directly back to the game after that. For all other apps hitting the back button a few times backs completely out of it and closes it, games dont work this way.
The only thing ive found that works so far is to go to the main menu of the game, and then press back until you are at the home screen.