It depends on where you are. Some places are very relaxed, some are very tense. If you're applying for a performance major, they'll probably ask to hear your solo repertoire, hear you sight read, play some scales, etc. It's pretty straight ahead.
I don't know what type of music degree you're applying for, but as a performance major i found that the only effect that it had on my entrance to Peabody was where I was placed for ear training. It's really just to see if you can hear pitch. If you aren't a good singer, it's not a big deal. Just as long as you prove that you aren't tone-deaf. I have a feeling that perhaps they will just factor it into your audition as well as a small percentage (i.e. "this guy is really really good, but he can't hear notes. lets accept him anyway." as opposed to "this guy is alright, but he can't hear notes. let's let in the guy who is alrlight and CAN hear notes") It's not about to see how good of a singer you are. So if you're no pixietricks it's all good
Probably basic stuff from "name the key signature" up to "what kind of chord is this" or "what is the form of this excerpt" or "find the voice leading errors" or i dunno, stuff like that. Musical examples with multiple choice answers seems familiar to me
It depends on where you're auditioning and what kind of degree you're majoring in. My schools told me what to play.
Thanks in advance