Arcade version
Hold [A] + [C] + [Start] on controller two after the title screen appears.
Arcade operator mode
Hold [X] + [Y] + [Z] + [Start] at the title screen. This will allow the difficulty level and credits to be adjusted.
Shadow mode
Hold [L] + [R] + [A] + [C] + [Y] at the title screen, then press [Start] to display the options menu. "Shadow Mode" and "M Stick Adjust" options will appear on the menu.