Ok this is what happend. Your new piston and sleeve seized. It happens , you then took the piston out (not needed , just free it next time). You can do this a number of ways , removing the heatsink and tapping a wooden dowell on it or anything that wont damage the piston top.

After that , put back together and refire.

What happened was your piston was stuck , you took apart and then tried to shove it into the sleeve dry after a seize , which is due to tight parts. Anyhow after it cools its not going to go as far into the sleeve anyhow.

Everything you saw was normal. Cleaning it is fine and gel can make for stickier parts. But its fine , I can sometimes get a seized piston unstuck by just turning it backwards by hand via the flywheel. Then you pull it back as far as possible , then onto the starter box and normally the full rotation is enough to get it fired back up and on track. You should maybe look into running the motor via the cyrul method for a tank or so to get things flushed out and get it loosened up a tad more.

Just a thought.