Hey folks. Looking at selling my iPhone12, as I got a 16 a few months ago. I've grasped the general consensus, but I just want to be triple sure before I sell it that it's essentially factory brand new, none of my data etc. I'm also wondering, if changing any settings on the iPhone12, is going to change anything on my iPhone 16?

EG: If I'm signing out of iCloud, am I then going to be signed out of iCloud on my 16? Or are settings that get changed specific to that phone only?

Ideally if someone has a "step by step" guide that would be awesome!

Thanks