Wow, it's been a while since I put in any of those codes (maybe 15 years now? Time flies...).

I remember I had them memorized: 19 65 9 17 would be the stage select (hold A while pressing Start, naturally),

4 1 2 6 would be to activate Super Sonic,

and...

...and...

...and I seem to have forgotten the Debug code. Waaah. Looks like it's time to brush up on my history again!