sonic-zilla
Enter the Options Menu and play these sounds on the SFX Option: 0, 2, 1, 1, 6, and 6. The screen should shake if you entered the code correctly.
anti-gravity sonic
Enter the Options Menu and play these sounds on the SFX Option: 0, 9, 0, 1, 6, and 8. The screen should shake if you entered the code correctly. Next, hold Buttons 1 and 2 and press Start.
skip to boss
Enter the Options Menu and play these sounds on the SFX Option: 0, 2, 1, 5, 6, and 6. The screen should shake if you entered the code correctly. Next, hold Buttons 1 and 2 and press Start
fast music
Enter the Options Menu and play these sounds on the SFX Option: 0, 4, 2, 5, 5, 7. The screen should shake if you entered the code correctly.