Is it legal for a cop to arrest another cop, or pull him over, like he/she would with a citizen?

yes. its actually happened several times. a few years ago, i believe in florida, a state trooper pulled over a cop driving at excessive speeds in their patrol car trying to get to their other job and pulled them out of the car at gunpoint. there was another case of a off duty officer at a bar trying to arrest a girl that wouldnt go out with him (or something i dont remember the exact circumstances. theres a video of it on youtube) and he was arrested.

Absolutely. Cops have been pulled over and arrested for DUI many times.

Of course it is legal, although much less likely. For example, a cop seeing another cop speeding is going to think that he is chasing somebody or racing to the scene of a crime, not illegally speeding.

N0- happens all the time just like a civilian can make a citizens arrest.

Yes, of course. It has happened many times already.

Completely legal and it happens.

No one is above the law except Hillary Clinton.