"New" b&s 21hp engine

So my mom blew up her motor in the mower we use to now the lawn and thankfully the warranty was still good and they replaced it. After some negotiation with Sears they let me keep the old motor. I have removed the flywheel and found the rotor, block, and the stator all broke. But even with all these off the engine still is a pain to get to turn over and sometimes only will backwards.
here's the flywheel with one of the magnets broken off and the rest scuffed bad.
This is the block with two bolts that used to hold the flywheel broke off.
I'm wondering what it could be internally that would cause it to lock like this.

could have thrown a counterbalance, the crank bearings could have worn, giving the crankshaft play and allowing it to rub on top, wrecking a whole host of stuff

I'm thinking it's something to do with the crank. I'm going to pull it apart this weekend hopefully and see what I can find is wrong.

if it was over-revved, the internal governor mech could have come apart too

Yeah I'm going to have to tear it apart because it only mowed my lawn like 4 times and was never over-revved. All I know is it ran one day I shut if off came back a couple days later and it was locked up. I got it to turn and started it but I heard a bad rattling noise so I shut it off.

probably crank bearings

Well I got to work on it today and noticed the only reason it still wasn't turning was the bottom shaft was rubbing the box. My flywheel that I ordered will be in soon and I'm going to have k2500lifes brother weld back in the mounts for the stator. I'm still waiting to order a replacement stator.

Pff you dont need no stator.

I know I don't need a stator but I want to keep one on there to charge the batterie and run the lights.