All Working Bio-hazard Battle Cheats - Sega Genesis

Level select
Hold [C] when the Sega logo appears. While holding [C] sweep the D-Pad in a clockwise full circle starting at [Up]. A sound will confirm correct code entry. Press [Start] to display the level select screen.

Unlimited lives
Enable the "Level select" code. Highlight the last level on the level select screen and press [A] + [B] + [C] + [Left]. Then, press [A] + [B] + [C] + [Left] again when the screen fades.

Fly same ship
Highlight the "2 Player" option at the main menu, hold [Right] and press [Start]. Release [Right] after the ship selection screen is displayed. The ship in the top right should be selected for each player.

Bonus level
Locate the caves immediately following the opponents that resemble a pair of lips. Move to the top left corner to lose the current ship and restart in a level consisting of a large asteroid field.