There maybe a number of reasons to go back to the stock ROM. We do not discuss them here :)
But what to do if you flashed something, wanting to go back to stock, and did not brick your Realme X2 yet? :) Here is super quick howto guide. There are o...
here is super quick howto for rooting your Realme X2 (any variant: CN, IN, EU).
Unlock phone's bootloader and boot fastboot mode
Flash custom recovery (currently the only available is TWRP). Do not reboot yet!!!
For Complete Root howto please read this post
Quick root howto for Realme X2
What is written below is for both CN and EU versions, but the files attached are for CN only!
Along with win and md5 files TWRP creates recovery.log file. If you look inside this file, you can see the full log of what TWRP has done. There you can notice that win file with the boot partition is in fact a result of the dd command, so that's ...
And the good news: the fingerprint sensor now works!!!
EDIT. Of course, after bootloader unlock :) It was working fine with locked bootloader even before :)