To go to the Home Screen, swipe up from the bottom edge of the screen (on an iPhone with Face ID) or press the Home button (on an iPhone with a Home button). Swipe left to browse apps on other Home Screen pages. Swipe left past all your Home Screen pages to see App Library, where your apps are organized by category. To open an app, tap its icon.
Check here first. Depending on the product, you can find its serial number in one or more of these ways: Check the surface of your product for a printed serial number. On Mac, choose Apple menu > About This Mac. On iPhone, iPad, iPod touch, or Apple Watch, go to Settings > General > About. If you use the Finder or iTunes to sync your device
On an iPhone 6S or earlier, press and hold the home button and power/lock buttons until you see the Apple logo. Don't bother swiping to power down if that option comes up, just keep holding those
To put your phone in DFU mode, open iTunes or Finder. One after another, press and release the volume up button, then the volume down button. Now, press and hold the side button until the screen turns black. While holding the side button, press and hold the volume down button. Wait five seconds, then release the side button but continue to hold
Open the iPhone by swinging the display up from the left side, like the back cover of a book. Don't try to fully separate the display yet, as several fragile ribbon cables still connect it to the iPhone's logic board. Prop the display up against something sturdy.
Solving "black screen" problem. If the black screen does not disappear, connect your phone to the charger and simultaneously press the two buttons: Home + Power key or Volume Down + Power button depends on what version of the device you are using. You ought to hold down both keys for about 10 seconds until the Apple logo appears on the screen.