---------- Post added at 10:41 PM ---------- Previous post was at 10:21 PM ----------
Thanks. I downloaded it and followed the instruction. It didn't work exactly the way you mentioned.
The zip file contains 3 folders. I had to copy the content of "Maincode" folder in the adb folder and then execute the codes.
I had problems after running "8909_fastboot_all_images.bat" file. It only restarted the devices. So some time after several tries I restarted the devices by holding the buttons and it finally did the magic.
Later OTA updater notified that there was a new update to "YT3-X50F_S000123_181225_ROW" which obviously I couldn't install because of TWRP.
Learning from experience I googled it and luckily found it on "lolinet" (Since I'm a new member I can't post links). Following your instructions everything went smoothly.
Hope others find this useful.
Did you find the OTA.zip to be applied using TRWP? Or you make it stock, and then apply all the updates?