Nope, users can go to sites like
GSCentral and find existing codes for games. People can edit/create their own codes themselves (like I do), but for the normal user, it's not really needed as codes come complete.
Here, some codes (PAR and GG converted to hex) for Sonic 2...
000344:6004 MASTER CODE (MUST BE ENTERED)
FFFFD0:0001 Enable Stage Select
FFFFD2:0001 Enable Debug Mode
FFFFB1:0007 Have All Chaos Emeralds
FFB02B:0002 Invincibility
FFFE12:0009 Infinite Lives
FFFE24:0007 Unlimited Time
FFFF73:0000 Play As Sonic & Tails
FFFF73:0001 Play As Sonic Only
FFFF73:0002 Play As Tails Only
FFFF73:0003 Play As "Weird" Tails Only
FFFE21:0001 Always Have 1 Rings
FFFE21:0032 Always Have 50 Rings
01217E:6004 Sonic Doesn't Lose Rings When Hit
012192:6004 Tails Doesn't Lose Rings When Hit
01ABEC:604E Super Sonic Doesn't Lose Rings With Time
FFFE19:0001 Sonic Looks Like Super Sonic (Disables Super Sonic)
FFB028:00FA Sonic Never Drowns
FFB068:00FA Tails Never Drowns
FFF64A:FFFF Disable Water On Levels
0041C0:31C4 Start Most Levels With Some Rings
0FCBBC:0000 The Regular Level Music Plays When Super Sonic
These are complete codes. No editing needed. Try them.
EDIT: Here, I convered them to Regen's .dat format in PAR/Hex form...
[0]
Name=MASTER CODE (MUST BE ENTERED)
0=Off
1=On,000344:6004
[1]
Name=Level Select
0=Off
1=Enable,FFFFD0:0001
2=Disable,FFFFD0:0000
[2]
Name=Debug Mode
0=Off
1=Enable,FFFFD2:0001
2=Disable,FFFFD2:0000
[3]
Name=Chaos Emerald Modifier
0=Off
1=None,FFFFB1:0000
1=One,FFFFB1:0001
1=Two,FFFFB1:0002
1=Three,FFFFB1:0003
1=Four,FFFFB1:0004
1=Five,FFFFB1:0005
1=Six,FFFFB1:0006
1=Seven,FFFFB1:0007
[4]
Name=Invincibility
0=Off
1=On,FFB02B:0002
[5]
Name=Infinite Lives
0=Off
1=On,FFFE12:0009
[6]
Name=Infinite Time
0=Off
1=On,FFFE24:0000
[7]
Name=Character Modifier
0=Off
1=Sonic And Tails,FFFF73:0000
2=Sonic,FFFF73:0001
3=Tails,FFFF73:0002
4="Weird" Tails,FFFF73:0003
[8]
Name=Rings Modifier
0=Off
1=1 Ring,FFFE21:0001
2=50 Rings,FFFE21:0032
3=100 Rings,FFFE21:0064
[9]
Name=Doesn't Lose Rings When Hit
0=Off
1=Sonic,01217E:6004
2=Tails,012192:6004
[10]
Name=Super Sonic Doesn't Lose Rings With Time
0=Off
1=On,01ABEC:604E
[11]
Name=Sonic Looks Like Super Sonic (Disables Super Sonic)
0=Off
1=On,FFFE19:0001
[12]
Name=The Regular Level Music Plays When Super Sonic
0=Off
1=On,0FCBBC:0000
[13]
Name=Never Drown
0=Off
1=Sonic,FFB028:00FA
2=Tails,FFB068:00FA
[14]
Name=Disable Water On Levels
0=Off
1=On,FFF64A:FFFF
[15]
Name=Start Most Levels With Some Rings
0=Off
1=On,0041C0:31C4