If you want all the rewards, when you put in your profile name type in '2ndsquad'. You will receive all rewards.
Old movie=not sure what it does.
Infinite ammunition=does what it says on the tin.
Elite squad=your squad never gets killed.
Authentic=the hardest possible gameplay.
note=every time you die, you will have to re-enter the cheats. To do so, go into the menu during gameplay and select 'cheats' in the bottom right corner. Voila, happy killing.