Just to be clear, I wasn't taking the piss out of you, just Apple. My iPhone 4S became rubbish following an update. About a year later it became somewhat better with a later update, so just stick in there.
I had the iPhone 4s and it became really slow when iOS 8 was released. When I looked it up online, it was widely accepted that you shouldn't update past iOS 7, and if you did - well tough, you've just ruined your phone. In one of the later versions of iOS 9 it improved a bit, but still wasn't as...
What happens if you do?
The great thing about Apple is that if the latest iOS is doesn't play well with your older device, you can simply uninstall it and go back to the older iOS. Right?