Unlock options in extra option menu
Every time basic mode is completed with a different character a new option will be unlocked, until the extra option menu is full.
Play as Pride
Successfully complete basic mode with seven different characters. He looks like an old Fokker, but has different moves.
Play as Mel
Successfully complete basic mode with eight different characters. She is the girl from shop mode and fights similarly to Julia.
100,000 credits for shop mode
If during the course of the game you manage to pick up item #103, which resembles a red turban, sell it for 100,000 credits in shop mode. This item seems to appear randomly.
Full pause screen
Pause the game and press X + Y.
Successfully complete basic mode with all characters, including Mel and Pride to unlock three new arenas exclusive to original mode. To access them, move the pointer left or right at the arena selection screen until it is off-screen. A large box with the "Extra Arena" message will appear. Select the desired extra arena. The arenas are a small room, a very narrow bridge over along drop, and a geometric (cubes stacked in weird patterns) arena.
At the beginning of the game where the logo Power Stone 2 starts to appear, quickly repeated press Start, X, Y, X, Y, Start, X, X, Start and when you hear a sound of a bird chirping, that means you have recieved all of the items in the shop window.
Use the MegaMan Buster as the Strongest Weapon
When you gain access to the MegaMan Buster, set it to a MiniBook Item(so you have a better chance of getting it). After getting it in the game, hold down the attack button for about a minute (until the light waves turn red). Then shoot, you should be able to get some one out of their transform state(because the shot is so strong).
NOTE: This gun can shoot four times, but when the Gun is fully charged it still has four shots, so dont worry about the gun energy.
Beating the Pharoh Walker
Use a character who is very acrobatic (Falcon works best), then, when fighting the sphinx, try to survive until it crouches down to spin. If you move quickly, you can jump on its' back to avoid the spin, and if you hit the guy in its' tail, you can jump into his seat and use the laser to shoot it in the head, taking up to 1/5 of its' life.