Replace engine it will not start

If you have the front tires off the ground and the transmission is in "park", when you rotate one wheel forward, the other one will spin backward.

Most likely the torque converter slid off the hub and got crushed by pulling the engine and transmission together with the bolts. Before the two are separated, it is good practice to place some small blocks, like little wedges of wood, under the teeth of the ring gear, to hold the torque converter in place. That also prevents it from drooping once the engine is pulled away. The front pump seal becomes hardened with heat and age, and the weight of the torque converter can crack that seal, then it will have a massive transmission fluid leak.

The torque converter itself is actually pretty tough. If its hub was not seated in the front pump, it is the pump that would be damaged. If you are lucky, only the flex plate bent far enough to allow the engine and transmission to be bolted together tightly. If that is the case, you will need to separate them again, enough to allow you to wrestle the torque converter and feel when it drops into place. Unfortunately, unless you can remove the torque converter and see obvious damage to the front pump, I do not know if there is a way to tell without removing it or without starting the engine and checking for a leak or lots of noise.

One clue you might consider is if the torque converter is not seated properly, and if the front pump did not get damaged, and if the flex plate bent to allow the transmission and engine to be bolted together, when you unbolt them, the flex plate will want to relax and straighten back out, and that should force the transmission and engine to separate perhaps up to an inch. Normally you have to tug, grunt, pry, and whine to get the two to start to separate, but a flex plate under that kind of stress will help them come apart. If you see that happen, I would be less worried about the transmission being damaged.

Even if the front pump in the transmission is damaged, that has nothing to do with the rear half of the transmission which includes the park lock assembly. When you shift out of "park", the two front wheels are free to rotate individually. What else turns or does not turn depends on which items have the most friction at that moment. Normally you can rotate one wheel either way and the other one will just sit there, but if you find the other wheel rotates the other direction, that is possible too, but much less common.

It is when it is in "park" that rotating one wheel one way forces the other wheel to go the other way. And, if you have one tire on the ground so it cannot rotate, you will not be able to turn the tire that is off the ground.