Pro Action Replay Codes:
Infinite Time - 00D2B9:00 -Datel
Infinite Lives - 00D298:09 -Viper187
Infinite Rings - 00D299:98 -Viper187
Better Invincibility - 00D3A9:15 -Rid
High Gravity 5 - 00D518:FF -iamstilllhiro111
Glider From Start - 00D502:13 -Battleman100
Invisible Sonic - 00D528:76 -Battleman100
Level Select: Zone - 00D295:0X -Datel
Activate enable switch after the first 2 title screens but before the level starts, after the level starts disable action replay, use with the next code.
Level Select: Act - 00D296:0Y -Datel
Activate enable switch after the first 2 title screens but before the level starts, after the level starts disable action replay, use with above code.

x, Zone y, Act
0 Underground 0 1
0 Underground 1 2
0 Underground 2 3
1 Sky High 0 1
1 Sky High 1 2
1 Sky High 2 3
2 Aqualake 0 1
2 Aqualake 1 2
2 Aqualake 2 3
3 Greenhills 0 1
3 Greenhills 1 2
3 Greenhills 2 3
4 Gimmick Mountain 0 1
4 Gimmick Mountain 1 2
4 Gimmick Mountain 2 3
5 Scrambled Egg 0 1
5 Scrambled Egg 1 2
5 Scrambled Egg 2 3
6 Crystal Egg 0 1
6 Crystal Egg 1 2
6 Crystal Egg 2 3

Game Genie Codes:
Infinite lives - 009-04F-3BE -Galoob
Invincible after 1 ring--except on act 3 - A78-92C-19E -Galoob
Each ring worth 2 points - 026-5ED-E6E -Galoob
Each ring worth 3 points - 036-5ED-E6E -Galoob
Each ring worth 4 points - 046-5ED-E6E -Galoob
Each ring worth 5 points - 056-5ED-E6E -Galoob
Each ring worth 6 points - 066-5ED-E6E -Galoob
Each ring worth 7 points - 076-5ED-E6E -Galoob
Each ring worth 8 points - 086-5ED-E6E -Galoob
Don't lose rings when hit - 3A7-E4C-2A2 -Galoob
Start with 1 life - 012-B8D-E66 -Galoob
Start with 5 lives - 052-B8D-E66 -Galoob
Start with 9 lives - 092-B8D-E66 -Galoob
Stop timer - 001-12D-3B7 -Galoob
Start on Act 2 - 3E2-E4D-3B4 + 012-E5D-E69 -Galoob
Start on Act 3 - 3E2-E4D-3B4 + 022-E5D-E69 -Galoob