Final answer:
To restart an iPhone without the passcode, connect it to a computer, open iTunes or Finder, put it into recovery mode, and select 'Restore'. This erases all content and settings but allows you to reset the iPhone to factory defaults.
Step-by-step explanation:
To restart an iPhone when you have forgotten the passcode and don't have a fingerprint set up, you will need to use iTunes or Finder to put your iPhone into recovery mode and then restore it. Here are the general steps:
- On a computer, open iTunes (on PCs or macOS Mojave and earlier) or Finder (on macOS Catalina and later).
- Connect your iPhone to the computer using a USB cable.
- Force restart your iPhone: for iPhones without a home button, quickly press and release the volume up button, then volume down, and then press and hold the side button until the recovery mode screen appears. For iPhones with a home button, press and hold the side (or top) button and the home button simultaneously until you see the recovery mode screen.
- Once your iPhone is in recovery mode, you'll get a prompt on iTunes or Finder to restore your iPhone.
- Click 'Restore' and wait for the process to finish. Your iPhone will be erased and reset to factory settings.
Remember, by restoring your iPhone, you'll erase all content and settings. If you have a backup, you can restore it after the process.