Bearings?....
I have a feeling, it's going to be worse than you think. Like Seadooya has said, if you put some PB or oil inside, loosen up the rings, it will let go of a light seize. But, if your not able to get it to break loose after a little setting for a few days, you may very well have a bad bearing.
I hate being the devils advocate, but even if you do free this up, you could have a flat spot on a roller ball bearing, cause this. The motor will run for another season or so (maybe), but then may start to cause more trouble.
From what I am seeing, your having a hard time to find a place to turn the motor over. Well, I see the head is off, so don't have to worry about pulling the plugs out. But, you should be able to reach behind the motor, pull off the grey shaft cover and grab the PTO and wiggle it from right to left.
If you have to use a pipewrench to break the seize.... I'd be wanting to pull and inspect the bottom end. Usually, a light seize is in the top end and is really easy to break.
If you don't want to pull the motor, you can consider pulling the 4 bolts in your cylinder jugs and removing them. Then, you'll be able to tell if it's a cylinder sticking or if you've got bottom end problems.
If you do pull the jugs, make sure you look at the base gasket. In the center, you'll see a series of holes. This determines the gasket thickness for your squish gap. You need to replace that base gasket with one of the same thickness.
I hope, by the time you read this, you've already got the motor to turn over......:cheers:
Oh, BTW... I almost forgot. If your starter is seized, the bendix is engaged to the motor, this will also make you think your motor is seized. So, make sure you check the starter......