iPhone 6S software issue

My phone has a glitch of some sort. I’ve backed everything up, did “restore” but the problem persists. I had been told to expect all of my apps, etc to disappear and it would look like it did out of the box, but they did not. Everything was there. What did I do wrong?
I would like to put entirely new OS software on but have heard varying protocol for doing it. Does anyone know the proper thing to do? THANK YOU!

What sort of glitch does your iPhone have? When restoring your iPhone, you first have turn off "Find My iPhone" which requires your Apple ID and password to verify. Once that has been done you can attach your phone to your Mac or PC and use iTunes to restore it. When restoring, iTunes will download and install the latest version of iOS to the phone. (iOS 11.2.1). Make sure you backup your phone to both iCloud and iTunes before restoring it.

Thank you. That is precisely what I did.
The glitch is that it flickers at the top of the screen and does not have any ability to allow the user to punch in the unlock code except after multiple tries that require restarting it. Even then it only lasts for a minute or so before becoming useless again. Curiously it did remain unlocked throughout the entire restoration process without locking up.

Further, the Apple store advised that if restored it would be to factory settings, which for the most part it was not. All of my apps were still on it, as were all of my texts,etc.

Upon further review, during the restore process you are given a choice of “restoring from a backup” or “set up as new iPhone”. I had chosen the first one. Perhaps if I chose the “new iPhone” option all would have turned out differently??

Your expert opinion is appreciated. Thank you!

Setting it up as a new iPhone means that all your apps and settings would have to be restored manually by you. And, that is likely not going to resolve the flickering problem. Did you at one time get the phone wet or drop it? I imagine your phone is no longer covered by the Apple warranty so it may be expensive to get it repaired by Apple. You might want to consider trading in your 6S for a newer phone.

chscag,
Thank you very much for your suggestions to help with my dilemma. I tried the "set up as a new iPhone" option as a last ditch effort to resolve anything that was wrong, to no avail. And no, the phone has not gotten wet, and the last time it was dropped was several months ago. I will indeed be getting a new phone tomorrow but doubt my old one has any trade in value. :-(