I think its just volume up held when power off on older devices (maybe volume down I dunno) whatever it takes to get the iTunes connect logo, NOT DFU mode where screen is off but phone recognized by computer... on 7/7+ you hold down vol down while booting up I recommend "reset all settings" NOT "reset all settings and data" before powering down and vol down to minimize chance of errors carrying over, etc. this will reset Location services privileges, Touch ID, etc. Then when it says you can restore or update, hold "alt-option" and click upgrade button and point to IPSW that is currently being signed (if its 10.1.1 for example, even though 10.2 is latest, still for now possible since 10.1.1 still being signed before they close window eventually). Upgrade button only applies for same OS or later OS as far as I know not downgrades even if signed. I was on 10.1.1 and "upgraded" to clean 10.1.1 go to www.ipsw.me for the IPSW of preference that is being signed once its done, rather than apple logo boot up it will just have a fade animation back into home screen this just did a clean restore to only the OS components, SHOULD resolve any aggregate OTA issues I have a friend who used to work at Apple Store, he said other employees had touch problem like my 7+ where it stops responding to touch randomly as a bug before locking and unlocking device I hope this resolves it for me too! anyways, hope this helps!