How to explain to teacher that I can't do something?
Folie a deux
Talk to your teacher and explain your dilema. If he's not willing to help you out in some way, talk to your counselor. It's not fair to assume all students have this technology available.
If he doesn't KNOW that you don't have a phone capable of doing all that, then for heaven's sake TELL him. He's not a mind reader.
Also, if you're in high school, you can have your parents contact him and tell him that you don't have a phone with that capability and you're not going to have one. It's very wrong for him to assume that all students have a smart phone.
Have a parent text him that you phone is old and doesn’t have that function.