You mean an Ariel?
Depends, I don't think you need to know it, it's more like a skill that will come along with the other tumbling you learn as time goes on. If you are going into level 1- you do not need to know an Ariel, but you should know how to do basic cartwheels and forward/backward rolls.
No, most cheer teams don't even teach ariels. Its more of a dance tumbling trick. You should try to learn, cartwheels, roundoffs, forward & backwards rolls, walkovers, spring etc. Also work on flexibility. Also an Ariel will be easy to learn with strength and power gained from other tumbling skills
Usually they don't make you since an ariel is a dancer trick. They'll want you to know whow to do things like a cartwheel, round off, back handspring, tucks, etc.
Those are called aerials. And actually, I don't really see them used much in cheer because they aren't worth a lot of points. I taught myself how to do them in my front yard because I'm a baton twirler, but I've never used them in cheer. They're nice to have, though.
That's an aerial and no you don't but their easy to learn and very impressive!