I have been completely happy with my iPhone 6S since the day I bought it in November 2015 until I made a stupid decision to upgrade to the latest iOS 11.3.1 from 10.xx something. I did the update about a week ago. Until about a week ago, I was on iOS 10. I don't really care about updating iOS as long as my phone is working fine which it was. But in a brief stupid moment, I updated it. And now my battery time has greatly reduced and the phone gets warm too for no reason. I was very happy with the last iOS version I had. Is there any way to easily and safely roll back to that version? A number of ways show up when you do a Google search but I'm not a techie and I don't want to screw things up. So I only want to follow a method which works flawlessly. How do I roll back to the last iOS version I had before the update?