Approve this iPhone

SOMEONE PLEASE HELP!!! I don’t understand how this works! I recently traded my iPhone 6s Plus in for another one because my original one kept freezing. After I got home I put my SIM card in and signed into iCloud. First off when I pressed restore backup it restored my older version and I don’t no how to get back my newer version (I tried everything!) now they want me to update Apple ID settings and I put my Apple ID password in then approve my iPhone from another device came up... however the screen was almost like frozen the words were off the screen. I tried everything I’m currently on the phone with them and I’ve been on hold for an hour! Please someone give me answers