Prologue: So I was looking forward to finally upgrading my 5s to a 7 this month, only to use iOS 10 and realize it's a trough of inconvenience, a brain-dead hamster of usability, and a Trump Hair of incoherent design. All around it's just a suit-wearing paraplegic Sasquatch gussied up by 1st-year cosmetology trainees. My question is, if I buy a used 6s (with iOS 9) from eBay/CL/Amz/or wherever, is it possible to do a factory reset when I get it without upgrading to iOS 10? I ask because if it's not possible, I'll hold off for future updates to 10 and see if Apple corrects the blatant inconsistencies with the design and function before spending money on a new iPhone. Thanks so much!