There was most likely nothing wrong with the engine except you had the throttle closed.

Also on a old unused engine, a valve will stick open and or a pushrod will jump out of position holding a valve open

To get the piston out, you have to heat up the case a little and push the cylinder sleeve up above the wrist pin extraction hole on the rear of the engine. You withdraw the wrist pin and then lift the cylinder sleeve and piston out of the engine.

I do not recommend you do this for everything will be stuck with hardened castor oil and difficult to get out.

To look at the ring will most likely do more harm than good?