How to get original Rotation and everything else?

I can't understand why you can apply rotations so they turn to 0 0 0.

Is that because it's easier to "apply" instead of going to the local origin thing? I think maybe and also this allows to reset other things to 0 0 0 and work easier with it, but okay hmm yes maybe you can work easier with it. IF you own the .blend file but if you import something, I think not...

My question is how can you, reset the rotation of an applied object "ACCURATELY". It is impossible for me to even imagine that in technical view, that a mesh has 0 0 0 when its position is completly somewhere else than the center. The original position or rotation or whatever has been done in math in the backend, holds the rotation value. How can I make that value display?