Be Invincible:
After pausing the game press rapidly: Black, White, Left Trigger, X, Left Trigger, White. A explosion signals correct code entry.
How to Get Costumes:
At different points through the game after certain missions you will automatically unlock the following costumes
Original
Golden Age
Silver Age Superman Red
Silver Age Superman Blue
The Return of Superman Black
Superman of the 90s
Kryptonian
Post-Our Worlds at War Mourning
Kingdom Come
Free Roam Mode:
After finishing mission 4 you will get Free Roam which allows you to replay any previously finished mission