Still stuck?
I've gotten a lot of engines un-stuck. Usually liquid wrench. What's stuck? Be careful on stuck valves, if you try to unstick them by turning the crankshaft you can bust something. Sometimes you get lucky when they have not been stuck that long, if there is a little movement just work it back and forth. If the piston is stuck you should remove it after you get it un-stuck. Chances are the rings are still stuck in the piston after piston is free in cylinder.
Sometimes heat can loosen things up. My most difficult piston for me was from a BMW R27. Soaked it with a bunch of stuff, heated it, finally ended up pounding it out with a very heavy hammer. Destroyed the piston, but I had no other choices...
http://www.cyclerestorer.com/pages/rest ... 4&td_var=8I've un-stuck pistons a few times when exhaust and intake valves are closed by putting a grease fitting in spark plug hole and using grease gun. 1200 psi....