During gameplay in Arcade or Rising modes press Up(2), Down(2), Left, Right, Left, Right, X, Circle to raise the number of continues to 573. The lives carry over across modes/characters until the game is quit through the PS3.
At the 'Title' screen press Up, Up, Down, Down, Left, Right, Left, Right, L3, R3. If you have entered the code correctly You will be able to purchase 30 lives on the 'Shop' menu for 57,300,000. This upgrade also becomes available when you complete the game.
During the level 1 loading screen (and before it ends) press Up(2), Down(2), Left, Right, Left, Right, Circle, X, Circle, X and the background music will change to a remix of the first level of Contra. If the code has been entered correctly you will hear a voice say 'Let's rock!' as confirmation.
During gameplay in Multiplayer mode after you lose your final life and your partner is still alive press Up(2), Down(2), Left, Right, Left, Right, Circle, X, Circle, X. If you entered the code correctly you will now come back with one last life in Arcade mode or two more lives in Rising mode.