The following are known Action Replay Codes for Sonic the Hedgehog on SEGA Genesis / Mega Drive (Genesis).

The codes should work with the region specified but may work for other regions as well.

Device Compatibility: Action Replay

• Enable Stage Select 1
  FFFFD0:0100
• Enable Debug Mode
  FFFFFA:0100
• Infinite Rings 2
  FFFE20:00C8
• Infinite Lives
  FFFE12:0009
• Stage/Act Modifier 3
  FFFE10:xxyy
• Makes Sonic Invulnerable To Enemies, Bullets, And Spikes Until He Picks Up Another Shield
  0039F0:11C1
• Aerial View of A Level 4
  0039FC:31C1
• Gives Sonic Turbo Shoes With Every TV He Breaks
  00A35E:6042
• Begin With Several Hundred Rings On Each Level 5
  003242:6010
• Begin The Game With 99 Lives
  00334A:0063
• Infinite Lives
  0138A0:6032
• Super Speed!
  FFF761:6411
• Invincibility (Enemies Can’t Touch You) 6
  FFD031:FF
• Invincibility (Always Have Shield)
  FFFE2C:00
• Invincibility (Starman Effect)
  FFFE2D:01
• Set Total Time To 0:01
  FFFE24:00
• Infinite Time Underwater For Sonic
  FFFE15:FA
• Defeat Stage 1 Robotnik Boss With 1 Hit
  FFD921:01
• Defeat Stage 2 Robotnik Boss With 1 Hit
  FFD821:01
• Defeat Stage 3 Robotnik Boss With 1 Hit
  FFDA21:01
• Defeat Stages 4 & 5 Robotnik Bosses With 1 Hit
  FFD861:01
• Defeat Final Stage Robotnik Boss With 1 Hit
  FFFE5F:01
• Set All Chaos Emeralds
  FFFE57:06
• Switch F/X On For Levitate Jump
  FFD012:FE
• Faster Music
  FFF001:00
• Hyper Mode (Sonic)
  FFD01E:00
• Sonic Color Modifier 7
  FFFB04:??
  FFFB05:??
  FFFB06:??
  FFFB07:??
  FFFB08:??
  FFFB09:??
  FFFB0A:??
  FFFB0B:??
• Sonic Sneaker Color Modifier (Base Color)
  FFFB19:??
  FFFB1A:??
  FFFB1B:??
• Warp To End of Stage 8
  FFD008:00

Footnotes

• At the title screen, hold the A button and push Start to enter the stage select menu.
• This code also allows you to pass the special stages with ease, and always get the Chaos Emerald at the end.
• Quantity Digits for “xx”(stage):

  00 – Green Hill
  01 – Labyrinth
  02 – Marble
  03 – Star Light
  04 – Spring Yard
  05 – Scrap Brain
  06 – ‘Zone’
  07 – Final (?)

  Quantity Digits for “yy”(act):

  00 – Act 1
  01 – Act 2
  02 – Act 3

  Not all stages have acts 2 or 3.

• You can also place objects by pressing Button A and placing them with Button C. When you’re finished press Button B and you’ll continue.
• When you press Start you’ll be prompted by a Level Select screen that enables you to choose any level.
• Switch effects off to collect rings.
• The third, fifth, and seventh lines are optional.
• Turn off after you reach there.