Yep takes 3 things to make a engine work. Spark, Fuel, Compression Loose
either one your pretty much screwed. and stuck Valves wouldn't have anything
to do with the hard starting.

Assuming you have a good spark when this happens, I'd try spritzing a little
fuel into the cylinder... it may identify a fuel related problem.

If fuel and spark and no joy, I'd be suspicious of stuck valves....

I'm betting on the fuel....