For what it’s worth I have purchased three iPhones thus far; an iPhone SE 1st gen, a 6s Plus and a 7 Plus. Only the SE was as expected (and I will never use it as a phone so I didn’t both testing the earpiece, speaker phone, etc). For the record ALL were in pretty great cosmetic condition. I was frankly shocked at how good they looked. Maybe some light scratches and minor dings at the corners.
The problem for both the 6s Plus and 7 plus were functional issues and battery health. Both had a battery of 77%. The 6s Plus had a busted speaker and the 7 Plus has a faulty ear piece (could barely hear it with volume all the way up).
So far Woot has been great and to be honest with each time the partial refund they offered would have been enough as I would have used it to just get a new battery but the other issues were unfortunately what caused me to have to return them. Well, I’m waiting on them to tell me if the vendor has a replacement for the 7 Plus but I’m not holding my breath.
YMMV.
I put my wife;s 6Plus in the drawer recently. She got a new SE. Her old phone tho was excellent. The battery life is very good, because it has a bigger battery. Of course now I think this model will not be capable of getting the next OS version. Still, this was a very good phone for her. I put it in service as a music storage device.
Any iphone that has iOS 13 will be able to update to iOS 14.
iOS 14 will be compatible with the 6s.