Computer Controlled Player
At the Character Selection screen, choose a character, then move the cursor to the red pearl. Now press X + Y + Z and the computer will take over your character.
Hidden Item Shop
Before the battle starts, move your cursor to BUY ITEM and press Y, A, Down, X, B. A tone will chime and give you access to the hidden item shop.
Buy enough items to access the second page of your inventory, then unequip all of your weapons. At this point the second page must be full. Now sell all your items starting with the last item on the second page. Eventually you'll reach a point where you're selling the same item multiple times. You can continue to sell it until you have all the money you need.
At the LOAD Menu, press L, Y, Right, R, R, A + START. This will allow you to jump to any scenario in the game.
Replay Old Missions
At the LOAD menu, press L, Y, Up, R, R, A. You can no replay any scenario you've played before.
At the PRESS START screen, press A, Z, Y, X, A, Z, X, Y.
Activate item shop:
Highlight the "Buy Item" option before a battle and press Y, A, Down, X, B. A sound will confirm correct code entry.
Press L, Y, Right, R(2), A + Start at the starting menu. To play any level already completed, press L, Y, R(2), A at the starting menu.
Press A, Z, Y, X, A, Z, X, Y at the starting menu. Then, press A or C to enter sound test mode. Press B to quit the sound test.
Purchase and collect items until a second page is displayed in the inventory. Remove all weapons and fill the second inventory page. Begin selling items starting at the last position on the second page. At some point the game will allow the same item to be sold multiple times. Continue selling this item to build your total funds.