Stage select:
Hold L1 + L2 + R1 + R2, then press Select at the main menu. The number will appear in the upper right corner of the screen. The left digit represents the stage. The right digit represents the time (day, evening, or night). Press Left or Right to change both values.

Fight as Kokopeli:
Select the password option from the main menu. Enter the following case-sensitive password:

zI2r6nXXXYgnHXXX
XffX3X3JAzmJZYXXII

A hidden robo fighter will now be selectable.

Fight as Zio Gagas:
Select the password option from the main menu. Enter the following case-sensitive password:

h%2SCvWSGWWWGXXXX
jfX3XnXjVXATaXXan

Fight as RB Green:
Select the password option from the main menu. Enter the following case-sensitive password:

XTYR3%KPWWWWGXXjX
ffXDXnjTkoZAYXX%M

Fight as Bad Ass:
Select the password option from the main menu. Enter the following case-sensitive password:

h%2SCvWSGWWWGXXXX
jfX3XnXjVXATaXXaN

Fight as Beta:
Select the password option from the main menu. Enter the following case-sensitive password:

X9y147OMUGWNGXXkX
fPX3Xn3jYWWWaXXdO

After the game begins, you will be upgraded with the best equipment, and will be able to access all of the different arms in the game

First place, all weapons:
Defeat Zio Gigas and enter the following case-sensitive password:

X57S6LWSWWWWWWWWW
WWWWW6TEnZJWaXXiX