Huh?Do not upgrade , do not upgrade, the iphone 5,5s, and 6 cannot fully handle the ios 10 update without lags or stalling software.
Yes,the iPhone 5 works fully normal with the latest iOS version,my mom has one,and it's absolutely lag free.Huh?
That's an iPhone 5 there in my pic, running 10.3.1. I've experienced no lag. Of course, if you're trying to do things like intense games on a 5 running 10.3.1 that might be why you say this, but that's not what I use my 5 for.