I think 9/10 becuse your shown you can show responsibility for having a big thing and your old enough. But when you have a disscusion just stay calm cause if you shout your parents will ignore you and that way you won't get them done cause your parents will think it won't be suitable for that cause you shout . So if you take the chat calmly your parents will probaly let you. Good luck
Whenever you're ready.
Whenever you are ready but most people go with 9 or 10 but you can do it whenever :)
I think when you leave school. I might be old fashioned but I fear in the rough and tumble of school an ear lobe could be torn.