Press these for getting all options instantly: Z, B, A, Left Shift, A, Z.
To view all of the credits without finishing the game, press in this combination: Z, left shift, A, Z, A, and Right Shift.
Reach the Sky Level
When at the Character Select screen and in Two-player Mode (two joypads must be plagged in), hold down the analog joystick and press kick (the bottom C button) simultaneously. You should be able to play in the sky (just like with the arcade version).
Glacious Infinite Combo
This is a real infinite combo. Use Glacious's liquidize and uppercut with a medium kick for the opener, and then press forward and fierce kick, keep repeating this and the combo will go on until the life bar is gone or the opponent breaks it (or unless your hands get tired). This can also be opened with the Cold Shoulder with a medium punch then forward and fierce kick. Thanks go to Willie Navarre for this code
At the character select screen (same as where you chose Gargos), press ZBAZAL. this code will automatically save, and will enable you to play as the black, gold, and white colors without the necessary training.
Play as Gargos
At the character select screen, where age, height, etc are shown, press ZARZAB. You will him him laugh if the code works.