[Guide] Unlock/Root/Update/Relock for BQ Aquaris X2 pro (zangyapro)

Introduction
I'm writing this thread to summarize useful information about the BQ Aquaris X2 pro such as:

1. preliminary actions (adb and fastboot configuration)
2. unlocking the bootloader
3. flash a factory image
4. root the device (currently without TWRP)
5. updating the device without losing root
6. relocking the bootloader

I own this phone since July 2018. I started writing my notes in August 2018 in the form of a Google document...

Read more