How many hours can I legally work on a weekend? (17 years old)?

There is no universal law that limits the time you can work on weekends. If you think that 20 hours over two days is a lot, welcome to the world.

that depends on the state you live in..... but really?.... welcome to the working world. if you arent willing to come in when asked then why did you even apply for the job? did you honestly think YOU got to pick your schedule?

Get another job and stop belly aching

A 17 year old can work no more than 8 hours per day on a non-school day and 4 hours on a school day. I would ask your boss about this.

well technically, you can work unlimited hours per day, however, you can only work 4.9 hours straight and then they have to give you exactly a 30 minute break, and then you can work for another 4.9 hours then they have to give you a 30 minute break, etc. i dont know where you live but this is the case for several northeast states such as where i live. but i know its different everywhere. ask your boss.