It depends on a variety of things like your availability, the time of the year (how busy it is), and how good of a worker you are. I know some people who get one 4h shift a week but there have been times where I've gotten 35+ in a week because I was free and the store was busy. Most managers I have heard give hours to those who they think deserve it.
Twice a month if you're in post secondary schooling or have any second job that they know of. About four times a week if you're in highschool.
You can either work one 4hr shift a week. Or up to 30 hours a week. They are not constant at all
25 or 30 hours
Anywhere from 10-25 hours a week