can I get instruction at apple when I buy a iphone?

Start here: https://support.apple.com/en-gb/guide/iphone/welcome/ios. You can also get an appointment at an Apple Store for help too. I would just go to the store and ask them about classes too.

I think you can do either. While I don't know if they'll be willing to give you an entire class at the Genius Bar unless it's a scheduled group class, if you have a specific set of questions you might be able to make an appointment. I've even had quick questions that could be handled without an appointment.