Xiaomi Redmi GO: unlock, TWRP and ROOT

Settings -> About phone -> tap 10x times Build number to become developer.
Settings -> System -> Developer options -> Automatic system updates -> OFF
Settings -> System -> Developer options -> OEM unlocking -> ON
Settings -> System -> Developer options -> USB debugging -> ON
Settings -> System -> Developer options -> Verify apps over USB -> OFF

Settings -> Security & location -> Google Play Protect ->  Scan device for security threats -> OFF

On PC (windows) install adb-setup-1.4.3.zip

on PC open Search menu (windows), type cmd in search, right click, Run as administrator
cd \
cd adb
cmd> fastboot devices
#should output one line with device ID if no line is here do not proceed.
#If windows see you phone (drivers installed properly) should output one line. 

reboot phone, hold vol- until Fastboot logo appears.
connect phone to PC with USB cable.
windows message device drivers succ. installed appears.


cmd> fastboot devices
#should output one line with device ID if no line is here do not proceed.
cmd> fastboot oem unlock-go

Phone reboots..
Long wait with phone on cable connected to PC until phone booted to OS.
It will reboot several times by itself.
Whole may take about 5 minutes.

Now phone booted to the OS, disconnect phone from PC, configure it again:
Settings -> About phone -> tap 10x times Build number to become developer.
Settings -> System -> Developer options -> Automatic system updates -> OFF
Settings -> System -> Developer options -> OEM unlocking -> ON (already unlocked)
Settings -> System -> Developer options -> USB debugging -> ON
Settings -> System -> Developer options -> Verify apps over USB -> OFF

Reboot your phone, hold vol- until Fastboot logo appears.
Connect your phone to PC with USB cable.

cmd> fastboot devices
#should output one line with device ID if no line is here do not proceed.
cmd> fastboot flashing unlock
cdm> fastboot flashing unlock_critical

Phone reboots again.
Erasing message appears.
Long wait with phone on cable connected to PC until phone booted to OS.
it will reboot several times by itself.
Encrypting message appears.
..
Whole may take about 5 minutes.

Now your phone booted to OS, configure it again:
Settings -> About phone -> tap 10x times Build number to become developer.
Settings -> System -> Developer options -> Automatic system updates -> OFF
Settings -> System -> Developer options -> OEM unlocking -> ON (already unlocked)
Settings -> System -> Developer options -> USB debugging -> ON
Settings -> System -> Developer options -> Verify apps over USB -> OFF

Done.

reboot phone, hold vol- until Fastboot logo appears.
connect phone to PC with USB cable.

on PC copy the twrp-3.3.0-0-tiare.img file to the C:/adb/ folder.

on PC open Search menu (windows), type cmd in search, right click, Run as administrator
cd \
cd adb
cmd> fastboot devices
#should output one line with device ID if no line is here do not proceed.
cmd> fastboot flash recovery twrp-3.3.0-0-tiare.img
Wait for extra 10 second here to flush internal sdcard cache.
cmd> fastboot reboot
#simultaneously with fastboot reboot command hold vol+ button,
we should to to TWRP right after flash it, or TWRP will disappear and we will need to flash it again.

Disconnect phone from PC.

TWRP> Reboot -> Power Off. (to turn phone off before installing microSD card)

Done.

Turn phone OFF.
Insert microSD,
Turn phone on.
Format flash as a 'Use as portable storage' inside the Android OS,
 dialog will appear right after boot with "'SD card': New SD card detected" mesage.
Turn phone OFF.

Done. Card prepared.

Extract microSD from the phone and plug it into the PC (again).
Transfer Magisk-v19.3.zip to microSD (any place you prefer).
Bring microSD card back into the phone.

Done.

reboot phone (if its off - turn it ON), hold vol+ until TWRP appears.
in TWRP:
TWRP> go to 'Backup'.
TWRP> Backup -> check all checkboxes EXCEPT /data
TWRP> tap on 'Select Storage' button and select 'MicroSD', tab 'OK' button.
TWRP> start backup.
Some error regarding /data will appear. Just ignore all the errors.
Make sure last line is blue one with:
"[BACKUP COMPLETED IN XXX SECONDS]", this indicates that backup is OK.
Wait for extra 30 second here to flush internal sdcard cache.

TWRP> Reboot -> Power Off. (turn phone off before rooting the phone)

Backup Done.

reboot phone (if its off - turn it ON), hold vol+ until TWRP appears.
in TWRP:
!!!!! TWRP> Mount -> check 'System', check 'Vendor', check 'Firmware', check 'MicroSD' (will be already checked) !!!!!!
!!!!! TWRP> Mount -> uncheck 'Cache'. !!!!!!
TWRP> "<-" physical button  to got to root TWRP menu.
TWRP> Install -> Up a Level -> /sdcard1 -> Select Magisk-v19.3.zip
#Errors will be reported: Fail to mount /data , /data/media , /data , /data/media/TWRP/.twrps , /data, Unable to mount storage.
Just ignore all the errors.
Wait for extra 30 second here to flush internal sdcard cache.
TWRP> Tap "<" physical button to got to root TWRP menu.
TWRP> Reboot -> System (to boot Android OS)

ROOT Done.