Entering DFU (Device Firmware Update) Mode In Iphone

1. First you should turn off your Iphone.
2. Press the power button to turn on the Iphone for few seconds,
3. Once you see the white the apple logo, press the home button at the same time with power button, the screen will glitch and white screen will appear for a moment,
4. After the 10 seconds release the power button but keep holding the Home Button.
5. After couple of seconds around 15 – 20 seconds, you will be in DFG Mode (you will see notification at right bottom about this state)
6. Once it was in DFU mode, the screen will be black.

Note:

DFU mode bypassed the current installed OS and allow you to upgrade or downgrade your OS.