'How do I remove the cylinder?'
Google 'strap spanner'. Once you get the idea you can make your own from a strong length of wood and a leather strap.
But.....Don't undo the cylinder if the piston isn't completely free first.
If the piston is stuck or even stiff in the bore then it will turn with the cylinder and twist the con rod. Then you'll be looking for a new one.
So first you need to take the back plate off and with a little heat and some kerosene you can free the engine up. Then some ATF to lubricate it... just like gazimoto said.
Then you can disassemble the engine if you really need to, but as gazimoto also said if you don't need to then you are better of avoiding that.
I'm sure you'll find that it will free up nicely and then, if it feels nice and bouncy with good compression, it will run fine.
good luck,
Dave H