Level 2:
Hold R on controller two and press Start on controller one at the title screen. McGlone Mine, Dino Park or Whitney Appliances may now be selected.

Level 3:
Hold L on controller two and press Start on controller one at the title screen. Gemini Towers, Shylock Center, or Paris Mine may now be selected.

Bonus mission:
Hold L + R on controller two and press Start on controller one at the title screen. This mission is based on the Deutschland Moldavia HQ level from the SNES game, The Peacekeepers.

Level 2:
Enter SSKD 0008 280G 84L2 as a password.

Level 2, last stage:
Enter SSK8 8038 LP88 5002 as a password.

Score over 4500 points in Missions 1 through 8.