Hello CG,
Welcome to the super quiet GenVibe website.
I know nothing about 2nd gen cars, I am a 1st gen guy.
However, a differential is the same in both gens.
Yes, both tires need to spin the same direction at the same time, thats how the car moves on the ground.
When you spin one tire and the other spins the other direction it is because of the open (not positraction) differential gears inside.
When you hold one and try to turn the other, the differential gears can't rotate, so the pinion (input) shaft needs to spin.
I am guessing your pinion shaft doesn't spin.
You mentioned missing bearings and metal debris.
The AWD cars are known to leak in the rear.
Mine does.
I check the rear diff level at each oil change, and wipe off the 90w drool.
I need to replace the seals some day.
I would say your differential ran dry, overheated, and locked up the pinion shaft in the case.
Try to turn the pinion shaft and let us know what happens.
If it doesn't turn you will need to replace the diff or rebuild it.
That is my amateur internet mechanics opinion and is worth exactly what you paid for it.

06 AWD/Abyss Black Mono/Loaded/Spoilers/Ground effects/172k/ 2025 Vibestock "Most Bling" Award
06 AWD/Lava Red Mono/Loaded/Spoilers/Ground effects/Leather/150k
05 Base/ Lava Red/ Daughters Car
06 Base/Gray/Totaled 5-24
03 Base/White/Totaled 1-23