Unlock Dural
Highlight Akira if you are using controller one or Jacky if you are using controller two. Then press Left and then Right on the D-Pad. Keep repeating this a few times and Dural will appear as a selectable character.

Unlock Alternate Costumes:
Hold 'Up' and then select your character with the A or C button.

Unlock Extra Character Selection Time:
At the 'Character Selection' Screen press Down, Up, Right, and A + Left for an extra 99 seconds of time.

Unlock Hidden Options:
At the 'Options' screen highlight 'Exit' and keep tapping Left repeatedly until another Options menu appears.

No Damage:
At the 'Options' screen hold B while highlighting player 1's life selection until the message 'No Damage' appears. Then press Start.