This can be completed in Tournament mode. First, max out all your stats for your character. In the My Character menu, press white. Then you will have the option to toggle the cheats on and off.
Unlockable
How to Unlock
Exrta Logos
Earn 10 exp points
Slow Motion Mode
Earn 20 exp points
God Mode
Earn 30 exp points
Choose any given letter by the game title you need to find Xbox cheats or Codes for.