- Windows Phone Internals (WPI for short - see the link below)
- FFU Image - Donor FFU may required : see https://lumiafirmware.com
- Good time enough - you will need it if something went wrong (anyway get PREPARED yourself pls)
Warning: Use Windows Phone Internals to unlock bootloader and take the phone to Mass Storage mode. Since you're accessing and MODIFYING to the file system, please DON'T make anything dumb. Otherwise your phone will be broken and you will need to reflash your phone and (may be?) start again this work. Before you restart your work, you may have to spend more ~1 hour bypassing the died Factory Reset Protection.