Drain the oil, replace the plug and wait a week to be sure that fuel is not getting into the Crankcase.
Remove spark plugs and turn it over a few times.
You may have the wrong dipstick, but fill it slowly until it indicates FULL and drive it!
Remove float bowl and jets. Pass a wire through all the holes. There are very tiny ones hidden on the threads of Float bowl jet on some models. Slide out the float pin, and carefully remove Float and Needle valve. Be prepared to close fuel line or valve. Re assemble and try it. New Premium Fuel.
Mowers with a Button can be fixed by removing the switch and connecting wires. Same BS that requires the stupid foot pedals for forward and reverse instead of a handy lever that also acts as cruise control.
Thank the STUPID people of the world for all this BS.
It is running lean but put that plastic Insulator back between Carb and Cylinder. It is there for a purpose.
You may have to drill out main jet a bit. Are you keeping engine shrouds in place/
Check that deck is mounted correctly. You may be able to loosen off the 2 nuts at the back of the deck if it is the model I am thinking of to give more slack. Note original placement.
Nasty situation. I would carefully drill a 1/8" hole at the very base of the Boss at the crack site all the way through the Flywheel until you find a replacement. Do not over tighten, use a New Key.
Try carefully heating one side of the boss with a propane torch. Then quench with cold water. Apply some penetrant spray for a few days. You could drill and tap it and install a smaller plug.. A sump pump is the best idea.
As suggested previously, determine which pulley is not rotating. Follow logical progression of belt around idlers and work pulleys. Worry about the Brakes later after you determine that they are fully released.
Remove and clean all Battery and starter Cable connections. Use a file/wire brush etc.
With Car or other 12VDC source OFF, connect + to Starter and - to Clean solid surface on engine like mounting bolts.
Work backwards from there....other side of solenoid etc.
NEVER TRY TO BOOST A SMALL ENGINE...
Looks like you ran out of Yellow Paint, or just started on the underside. A good choice would be Pickup Box Rhino coating after getting it sandblasted ( SP3 Commercial Blast.) Washing the underside is a waste of time and clippings act as a blotter promoting corrosion. Run it up on a ramp and...
Do the basics. Turn off gas if you have a valve for that. Remove Fuel Filter and drain old gas and dirt from Fuel tank.
Carefully remove float bowl and empty it. Replace Bowl. Fill with filtered Premium Fuel. If gas comes out freely, install new fuel filter. Blow into fuel tank and watch...
Take the top off down to the Flywheel and check under that nut to be sure that the Key has not been partially sheared which puts it out of time enough to do that . Did you remove the flywheel and examine the key? Set coil at 0.300" from Flywheel. It could be valve timing