If you have a spare plug, instead of pulling each plug, you can just pull the plug cap, insert your extra plug and confirm that you have spark at that plug by holding the plug to the engine case as you try to crank it. If you have spark at all four, then spark is probably not your issue. So, next check your gas.
Check your float bowls next to make sure there's gas in each one. If #3 is overflowing, then you either need to remeasure the float height there or, as you said, check to see if the float is stuck.
If you determine you're getting gas, then remove the air box and confirm that pulling the cable to full choke is actually completely closing the butterfly valves. If they aren't, you can actually manually close them fully with your fingers just so you can try starting them again.
If all of that doesn't work, try posting a video of it trying to start and maybe someone will notice something that you don't.