The following are known Game Genie Codes for Sonic the Hedgehog 2 on SEGA Game Gear.

• Infinite Lives
  009-04F-3BE
• Invincible After 1 Ring (Except On Act 3)
  A78-92C-19E
• Each Ring Worth 2 Points
  026-5ED-E6E
• Each Ring Worth 3 Points
  036-5ED-E6E
• Each Ring Worth 4 Points
  046-5ED-E6E
• Each Ring Worth 5 Points
  056-5ED-E6E
• Each Ring Worth 6 Points
  066-5ED-E6E
• Each Ring Worth 7 Points
  076-5ED-E6E
• Each Ring Worth 8 Points
  086-5ED-E6E
• Don’t Lose Rings When Hit
  3A7-E4C-2A2
• Start With 1 Life
  012-B8D-E66
• Start With 5 Lives
  052-B8D-E66
• Start With 9 Lives
  092-B8D-E66
• Stop Timer
  001-12D-3B7
• Start On Act 2
  3E2-E4D-3B4
  012-E5D-E69
• Start On Act 3
  3E2-E4D-3B4
  022-E5D-E69