What happens if a minor fights a adult but the minor starts it?
Will the minor go to juvenile detention?
It depends entirely on the circumstances. Factors that will play in include: were any weapons involved; the injuries inflicted; the behavior of the parties leading up to the fight; relative sizes of the parties involved; prior records; etc.
There is no easy way to generalize. A slender 15 year old fighting a husky/strong 20 year old, for example, is a very different circumstance or situation than a strong 15 year old who has studied tae kwon do fighting a frail 55-year old. A minor with a rap sheet or prior history of violence is more likely to be imprisoned than one for whom this is a first offense. A criminal defense attorney who is retained by the minor or the minor's parents and who can review all the circumstances in detail can provide an informed answer.