Wanna get to the end fast? Well beat the first scenario first. After completing that, you can return to the title screen and enter these codes to unlock the last stages. You can only unlock the scenarios in order.
Eighth Scenario - Right, Down, Up, Left, Circle, X, L, R
Ninth Scenario - L, R, Left, Right, Square, Circle, X, Triangle
Tenth Scenario - Triangle, Down, Circle, Left, X, Up, Square, Right