Hard Reset APPLE iPhone 6 Plus

• First you should to go to Home screen.
• Next scroll to Settings.
• Tap General.
• Select Reset, and select option "Erase All Content and Settings".
• Then you will see information to confirm.
• If promted, then enter your passcode.
• Confirm your choice and wait to finish operation.
• Done

Second Method

• Connect your iPhone to the computer and open iTunes.
• Now choose your iPhone from the left menu in iTunes.
• Then click the Restore button in iTunes.
  * You can now do back up your files, just if you want.
• After that please confirm information about this procedure -> click Restore.
• Next you will see, that iTunes will download, prepare and restore the software on your iPhone.
• In the end choose "Set up as a new iPhone".
• Enter a name for your phone.
• Well done!

Third method:

• You should to Plug your iPhone into your PC, or laptop.
• Power off your device.
• Then hold the Power button for about 3 seconds.
• Now press and hold Home button with Power button for about 10 seconds.
• After that release only Power button.
• Release Home button, when you are alerted by iTunes saying that it has detected a device in Recovery Mode.
• Confirm this, and wait until iTunes will restore your handset.