Successfully complete and save the game on the hard difficulty setting to unlock an "Extra 2" option at the main menu.
Game Shark Codes
Master Code (Must Be On) EC902CAC 1456E60A
Infinite Health 4CDF2F60 145608B54CDF2F68 145608B5
Infinite Time 4CDF2F60 1456FFB5
99,999,999 Points 1CF1D120 1DBC9E0C