Welcome to the forums. Someone will come along soon who has rebuilt many of the older four stroke engines..One person comes to mind who just did a complete rebuild on one..
I myself have torn down many an older two stroke engine for top ends, and splt cases for bottom ends that were bad, but they would still turn over fine,,not recommended though,lol! I would get the machine up in the air first and check and make sure that nothing is froze in the drivetrain first, and check for being able to shift the machine into neutral to let the wheels turn to take that off my list, even go as far to having a known good battery in the machine so it will light up the neutral light to help diagnose the issue. Then go to the top end from there would be how I would do it. Any top end that I ever had a meltdown with I could still turn over, it was just scuffed in the cylinder, or a hole in the piston that caused the issue. I've had bad crank bearings also where the engine would still turn also so I would start with what I suggested, unless someone who has worked on these allot has another suggestion. If the piston were actually stuck in the bore from sitting a long time and possibly rusted tight, it could be tough to get the cylinder off. I would get some oil down into the cylinder through the plug hole in the meantime. Good luck.
05 Suzuki DR650, Mikuni TM40 flatslide pumper carb,JE 10.5:1 piston,stage 2#190 Webcam,open airbox, Twin Air,full FMF system,Pingel fuel valve,Ricor Racing rear shock, Ricor Racing fork Intiminators, Progressive springs, Sargeant seat,DRZ250 tailight,custom plate,LED's,GPS,sumo fender,PT bars,Cycra brushguards IMS lowered pegs, aluminum skid,bearing chain roller,Pirelli,tank bag(gone)
06 Zuk KQ700, Kenda Bearclaw HTR radials Warn RT25 w/ syn. line, 1.5mm clutch shims