At the "Press Start" screen, press Up(2), Down(2), Left, Right, Left, Right, L3, R3 to unlock the Uprising R (30 lives) in the Customization shop.
While playing a game in Multiplayer mode, press Up(2), Down(2), Left, Right, Left, Right, Circle, X after you lose your final life and your partner is still alive. You will resume with one last life in Arcade mode or two more lives in Rising mode.
At the Level 1 loading screen (and before it ends), press Up(2), Down(2), Left, Right, Left, Right, Circle, X to change the background music to a remix of the first level from Contra. If you entered the code correctly, the comment "Let's rock!" will be spoken.
Successfully complete the game to be able to purchase 30 lives at the upgrade shop for 53 million CP.
Get a plasma gun (H), and save it until the second mini-Boss. Go to the right side, charge the plasma gun, then crouch and fire towards the alligators, and kill all of them. While doing this, shoot the gun horizontally at all bombs that the helicopter drops to increase your combo. Fire vertically when a bomb falls overhead, but do not shoot the helicopter. You can build a 60 combo and get approximately 50 million CP before the combo meter stops. When you start earning negative points, intentionally die, restart the level, and repeat the process.