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You cant, but you can buy them. Go google up the list of region-free xbox 360 games!
Chances are anything in the Indie section
You can find a list of Xbox games which will work on the Xbox 360.
If you game isnt on the list, then it will not work.
As long as the game and the xbox has the same region encoding then yes you can
Not all xbox games work on the 360. But heres a website with a list of xbox games that work