At a workplace you report it to the manager. At a college you report it to a dean or staff member. In general you report it to the authorities. I can't speak for Canada, but in the US, harassment is a criminal offense even if it is a minor harassing an adult.
Yup. Whether the harasser is a minor or not you can take the same steps you would take if you were minor, or if another legal adult were harassing you.
It also depends on the situation. If you're only being harassed online, you can easily block them. And sometimes the authorities (whether it be the police or management) can't do anything, so first try to take steps yourself to alleviate the problem.
That depends on the context really. If it is in some kind of controlled setting like a workplace or a school, you can report it to the people in charge of taking disciplinary action. If it is in a public place, you take it to the people whose job it is to take disciplinary action in public places, viz. the police. A little more information about how you are being harassed and where would help to generate a more informed response though.
And you can do all this even if it's a minor? The police won't say they can't take care of it because there not old enough and that since your the adult, you can take care of it? Thats what I think would happen so I don't know, thats why I'm asking. And I haven't been harassed by a minor. It's just someting I thought of to post. I mean it might help someone else who might be. Or it might help me if I'm ever in that situation. I don't mean online, but like at a work place, college or just simply outside or in my buliding downstairs.
Then, you can file a suit if you want...or just tell their parents.