E2E13. That'll get you to the third board on 1943 for the NES. Shit gets real on the third board, forget about the first two.
Down, R, Up, L, Y, B to play as same character on SF2
PAUSE, -UP-UP-DN-DN-L-R-L-R-B-A - ALL UPGRADES ACTIVE - GRADIUS III, SNES
HOLD -L, -A-A-A START - 30 LIVES - GRADIUS III, SNES
OPTION MODE, DIFFICULTY LEVEL, RAPID TAP -A - ARCADE DIFFICULTY LEVEL - GRADIUS III, SNES
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Hold Right B,B,B, then press Up B,B,B,Left,B,B,B,Down,B,B,B,Start