iPhone 6S Factory Reset From Settings
https://gsmfixer.blogspot.com/2016/03/iphone-6s-factory-reset-from-settings.html
Here is a method to factory restore Apple iPhone 6S to default settings. You have to reset iPhone 6S when there is a problem in processing of you have forgotten some security locks etc. This operation will remove all the data save in your phone so keep a backup before doing this operation. In this post we have given the method to hard reset iPhone 6S from the phone settings and we will share the other methods soon.
Open Settings >> General.
Now choose Reset, and select option "Erase All Content and Settings".
You will see warning of confirmation.
Enter your pass-code if promted.
Accept all and wait until the operation if completed