Is it okay to ask a potential future employer what hours I'd be applying for?

Remember that you should not be a slave to any interview. When you apply for a job, you not only have to look good enough to hire but the job should also look good enough to work for. So yes, you have every right to know what you will/would be doing, how much you'd be getting paid, and anything else the job expects of/from you. Jobs have their limits on what they're looking for so should you. Even if you're in a desperate situation you still have a right to know.

Yes, and most of the time, there is a place on most apps that have a simple little area that asks this question. They should want to know your availability so they do not sceduel you when you can't be there!

yes its ok. if they can't tell you then you should find another job