If you have a pulsating on stopping is an indication they are warped. They would have to be checked with a micrometer to tell if they can be resurfaced.
Visual inspection with outside micrometer. They should not be glazed, pitted, or thinner than the allowable minimum as measured with the micrometer.
There will be a pulsating on braking.
There is a pulsating on braking.
Yep.
Grinding
could be bad rotors, or brake pads wearing unevenly, which would result in bad rotors.
Bad rotors
If you have a pulsation on stopping the rotors are warped. They will need to be checked with a micrometer to determine if they can be resurfaced of discarded. The government set the regulations.
No just the bad one.
what do brakes look like when they go bad, how far can rotors go?
You do not rotate rotors. Replace a bad rotor or have it machined if possible. Never rotate them to another wheel location.
if your rotors r worn you see little groves on them that go all the way around these grove tend to have a rust color