I buy refurbished, unlocked smartphones and try to use them as long as possible with a discount MVNO for service.
Right now, I have an unlocked iPhone 4s running iOS 7.0.6 (11B651). I'd like to try upgrading to iOS 9 so that I can use some apps that require it. However, my research has turned up reports of iOS9 being quite slow on an iPhone 4s. While the benchmarks are useful, it's hard to know how frustrating it will be to have that kind of performance day-to-day without trying it.
So is it possible to try iOS 9 on my phone and revert back to iOS 7 if it is unbearable? If so, how does one do it?
