I never completed Sonic 2 properly. The Christmas I got it, I remember vividly. I was 9 years old, I got a Mega Drive (with Sonic and Mega Games 1), a TV (Matsui, Curry's pseudo-Japanese brand), and Sonic 2. Didn't come from a well-off family at all so it was a gobsmacking thing.
Dad set it up and he wanted to play "football" on it and as we were both huge football fans, I had no problem. Thing was, the game was World Cup Italia 90. Think it took us 20 mins to both agree it was terrible and I was left to myself to play Sonic 2.
Emerald Zone Act 1 and 2 despatched with no fuss, as was Chemical Plant Zone Act 1. Chemical Plant Zone Act 2... now we have a problem. Just before the boss, the pink liquid rises up and you have to get up and over it onto a bit where a moving platform slides across. Miss the platform and you go tumbling down into the liquid again, and have to work your way back up these moving block things that can also make you lose a life by effectively crushing you. Don't get up and out of it quick enough and you drown.
I looked for air bubbles like in Labyrinth Zone, but it's chemicals. I cannot time landing on the platform, at all. The countdown music. The drowning noise. Over and over again... I need to get ready to visit family, but I can't sodding do this bit. So, basically, since that despite the odd few goes at it and failing it, I gave up. Angry at my cack-handedness. How could I not get past the second bloody level on one aspect? Sonic 2 gathered dust on the shelf for a bit. However... the old level select cheat eventually came to pass (done through the sound test in options, probably read about it in Sega Power). I didn't take the mick, I went straight onto Aquatic Ruin Zone (3rd level) and continued on my merry way to finishing it. But the head-hanging shame of cheating never wore off.
So Sonic Mania comes along, remixed levels, remixed music... remixed Chemical Plant Zone as a pissing second level. They're going to put that bit in I couldn't do aren't they? They're going to do that. And replicate it perfectly, they did. And yes, I was still crap at it. Nevertheless, there was no way I was succumbing to it this time. No way. This time round, you're not bloody beating me. No chance. Don't Google for a level select cheat, this is our time now.
Anyway, after nine attempts. It was done. There was shouting, there was a fist-pump, there was swearing abound. My housemate wondered what the celebration was. When I explained, he was like "well the easiest way was to walk onto the platform rather than jump on it."
I was terrible at both disciplines involved in that bit, but Sonic Mania finally put that all to bed.