Motivation:

You want to sell or give away your iPhone. You want to ensure that the new owner will not access any of your data.

You may also need to give your iPhone to a technician to fix the broken display of your iPhone. You want to ensure that the technician cannot access any of your data.

You may also have so many buggy applications on your iPhone and want to increase stability and performance of your iOS.

Procedure:

• Import your Photos to a MacBook.
• Create a backup of data. It is best to let your iPhone synchronize everything with iCloud, including Photos and Contacts.
• Turn off Find My iPhone.
• Plug your iPhone to a MacBook.
• Open Finder. Click on your iPhone on the left panel.
• Click Restore iPhone… button.
• Click Backup button.
• Click Restore and Update button. Click Next button. Click Agree button.
• Follow the instructions to install a clean iOS to your iPhone.

Post Installation Configuration:

• Setup your iPhone.
• Activate your iPhone.
• Setup Face ID.
• Restore your Apps & Data from iCloud backup.
• Synchronize music to your iPhone.
• Go to Settings > Generals > Software Update > Automatic Updates. Turn off Automatic Updates.
• Go to Settings > Generals > Display & Brightness > Text Size. Drag the slider to the right to increase text size.
• Go to Settings > Messages. Enable iMessage.