Back tire won't turn in the reverse direction

If you have brake shoes then the could have come loose and be binding in the reverse direction, take the drums off and inspect!

A couple points here:
it is probably just the tire rubbing on the inside of a wheel well. Have a tire shop or mechanic check for wear of suspension components. Excessive wear on suspension arm bushings, ball joints, struts, etc. could cause "slop" or excessive travel forward and back which is not normal.
Itis also good practice to NEVER turn to steering all the way to the stops in any four or all-wheel drive vehicle.

it appears that the brake is faulty and when in forward direction is putting itself on. It is free in reverse. check the brakes are in good condition and properly retained

A wire is usually broken in the hinge area. You can make it go up temporarily using a common 9 volt battery and alligator clips directly on the motor reverse polarity to reverse direction.

brakes locked up did you use your emergency brake if so then you need to take your rear tires of and unlock your back brakes

Did you try direct 12vdc power to motor wires ? Reverse polarity should change direction of motor, then you'll know it's switch related or whatever. Did old motor do same? The switch reverses polarity, or is supposed to. If a motor goes in one direction, when wired backward ( reverse polarity) it should go opposite direction. That tells you motor is fine.

Sounds like you have a stuck caliper, they run $35-50 for the rears on that vehicle, They are not that difficult to replace, just be sure to bleed the brakes well after replacing it and check for leaks. If it has been like this for a long while. I would inspect the brake pads, and rotor while your there and replace them if they are worn.

sounds like the tracking rod may be broken or loose.

You may find it easier to remove the left front tire, if possible. If not turn the wheel all the way to the right. Remove the inner fender well, there are numerous 7mm bolts holding it on from under the spoiler area and around the front of the tire opening. There is one push style clip at the very top, just pull or lightly pry out. Look inside the opening to the tranny. Just above the axle shaft to the front there is the reverse switch. It is a plastic (white or black) body with a metal socket base, there are 2 wires going to it, remove the connector. Use a deep 19mm or 3/4" socket or a short wrench to remove the switch. Reverse the process.

Hmmm,. very interesting...

I have to throw this out there,. there are some certain tires which can only be put on so that thye spin in only one direction, if put onto the rims reversed, they will create havoc (and excessive wear),. I forget what the name of this style of tires are called, but they do exist..

ok here also you can tell if you have these kind of tires as it is like running your hand over a pet petting the back of a dog from head towards **** - its fairly smooth -- and when you run your hand back up towards the neck you get resistance and the hair stands up - ie not as smooth of a feel as the other direction... this is true with these tires.

I'm curious to see how this one pans out...

Best regards
Ck