How to make sure iphone is not remotely managed while buying a used one.
A friend of mine bought a used iPhone like 6s months ago. I was there to help the purchase, we checked everything, did software reset etc. and everything was just fine. He has been using it all this time and had no problems whats so ever. Recently, he wanted to sell it to upgrade and so he did the reset again to wipe the data out, and now it is stuck on Remote Management screen. We contacted the seller, and he said that at the time of purchase resetting made it 100% sure that it was not any sort of remote management, on the other hand my friend is saying that he just used it all the time and was never done any such thing. So, who could be wrong here, the seller or my friend. And how do I make it sure to avoid such situation in future while buying an used iPhone. I was under the impression that software reset is the thing to make sure that phone is not iCloud locked but this remote management is something new to me. Please guide. Thanks
iPhone 6s, iOS 11.3.1