In the Throg Breeding Facility you'll find a secret entrance to the "Lost City". Look for it in the lower right-hand corner of the map. You'll need to break through three or four secret doors to find this exit, but it's well worth it.

Highlight "REVIEW MISSION", hold SQUARE, and press CIRCLE, X, TRIANGLE. Release SQUARE, hold CIRCLE, and press SQUARE, X, TRIANGLE. The word "Cheater" should appear at the top of your screen.

For invincibility, pause the game and highlight "Sound Volume". Then push d-pad RIGHT and press CIRCLE, SQUARE, X. (If entered correctly, then the word "cheater" will appear at the top of the screen.)

Start a mission as normal. When you transport in, pause the game to bring up the sub-menu. Highlight Review Mission, hold CIRCLE, press SQUARE, release; hold TRIANGLE, press X, release; hold CIRCLE, press X, release; hold X, press SQUARE, release. The word Cheater should appear to confirm the code.

Start a mission as normal. When you transport in, pause the game to bring up the sub-menu. Highlight Review Mission, then, hold T, press CIRCLE, SQUARE, SQUARE, CIRCLE, release T, then hold X, press TRIANGLE, TRIANGLE. The word Cheater should appear at the top to confirm the trick worked.