At a guess, you suffered chain suck where the chain got stuck between the smaller chain-ring and the frame, or you dropped the chain between the rear cassette and spokes. The forces you then used have possibly been more than the QR skewers could handle and the rear wheel slipped in its mount. The weird force is the tire rubbing the frame.
My real concern is the "However hard I tried....." - you may have done significant damage to drive train components. Never put pressure on a jammed drive train - a modern bike is actually a very highly tuned, lightweight and fragile piece of machinery. Forces it is not designed to take will break it.
You do not say how you went from jammed and not moving to moving and not driving - was there a bang/crack/snap involved?
There are a few things that can be wrong, and based on what you said, you probably now have more than one fault. You need to isolate parts to find out what it is. Most of the of these checks can be done almost instantly without removing anything. The chain will get in the way - you won't need to remove it though.
Remove the wheel from the bike and check the freewheel. It should be
moving freely in one direction and locked up in the other
Check the rear derailleur - is the chain running freely though it.
If not, check the chain line and make sure the small sprockets are
Check the chain line though the front end. Is the chain clear of the
derailleur and sitting properly on the chain ring.
Spin the pedals and check the bottom bracket is not jammed up
somehow. check the pedals and cranks are properly aligned and
attached to the bottom bracket.