It depends on the rules the class has. Some classes have to get your parents' consent in order to enroll you if you're below their minumum age of consent. Some do not have such requirements. Check around first.
They should work out some arrangement. Normally this could be some consent papers or power of attorney from you parents. Guardianship could also be assigned.
To enroll in any school you need to have your parents signature, so if your parents aren't with you you will need to have a guardian sign.
18, or 17 wth parental consent
children can enroll in school anywhere froam ages 4-5, depending on the school district
yes you can
If you're in the US... Can you move out by yourself? No. Can you move somewhere else, such as a relative's house? Yes, but unless your parents give them some type of temporary custody they wouldn't be able to do things such as enroll you in school, seek medical treatment for you, etc.
Unless you are enrolling them in your own school and are getting a Home-Educator license, then no. If not, then it is illegal for to not be getting any education at all.
The legal age to move out is 17, but you can not un enroll from school. Only the person who enrolled you can un enroll you, unless emancipated.