Reset iPhone SE: Press and hold the On/Off Sleep/Wake button and the Home button at
the same time for at least ten seconds, until the Apple logo appears.
Erase your device with recovery mode
If you've never synced with iTunes or set up Find My iPhone in iCloud, you'll need to use recovery mode to restore your device. This will erase the device and its passcode.
Connect your iOS device to your computer and open iTunes.
While your device is connected, force restart it: Press and hold the Sleep/Wake and Home buttons at the same time. Don't let go when you see the Apple logo — keep holding until you see the recovery mode screen.
When you see the option to Restore or Update, choose Restore.
iTunes will download software for your device. If it takes more than 15 minutes, your device will exit recovery mode and you'll need to repeat steps 2 and 3. Wait for the process to finish.
Restarting and Resetting iPhone SE ios9 / ios10
Restart or reset iPhone - Reset fingerprint
If something isn’t working right, try restarting iPhone, forcing an app to quit, or resetting iPhone.
Restart iPhone. Hold down the Sleep/Wake button until the red slider appears. Slide your finger across the slider to turn off iPhone. To turn iPhone back on, hold down the Sleep/Wake button until the Apple logo appears.
Force an app to quit. From the Home screen, double-click the Home button and swipe upwards on the app screen.
If you can’t turn off iPhone or if the problem continues, you may need to reset iPhone. Do this only if you’re unable to restart your iPhone.
Reset iPhone. Hold down the Sleep/Wake button and the Home button at the same time for at least ten seconds, until the Apple logo appears.
You can reset the word dictionary, network settings, home screen layout, and location warnings. You can also erase all of your content and settings.
Reset iPhone settings. Go to Settings > General > Reset, then choose an option:
Reset All Settings: All your preferences and settings are reset.
Erase All Content and Settings: Your information, and settings are removed. iPhone cannot be used until it’s set up again.
Reset Network Settings: When you reset network settings, previously used networks and VPN settings that weren’t installed by a configuration profile are removed. (To remove VPN settings installed by a configuration profile, go to Settings > General > Profile, then select the profile and tap Remove. This also removes other settings or accounts provided by the profile.) Wi-Fi is turned off and then back on, disconnecting you from any network you’re on. The Wi-Fi and “Ask to Join Networks” settings remain turned on.
Reset Keyboard Dictionary: You add words to the keyboard dictionary by rejecting words iPhone suggests as you type. Resetting the keyboard dictionary erases all words you’ve added.
Reset Home Screen Layout: Returns the built-in apps to their original layout on the Home screen.
Reset Location & Privacy: Resets the location services and privacy settings to their factory defaults.
Force quit an application: Press and hold the On/Off Sleep/Wake button on top of iPhone for a few seconds until a red slider appears, then press and hold the Home button until the application quits. On iPhone 3GS or later, you can also remove an application from the recents list to force it to quit.