Flash Root Xiaomi Redmi3Pro/Prime IDO (Tutorial December 2017) on Windows PC.

Two steps: Prep laptop and Prep the phone.

Prep Laptop

1. Restart windows with disabled driver signature check.
Step by step (with picture) is in the following link
https://www.foldertips.com/android/cara-disable-driver-signature-windows/

2. Install Qualcomm Driver HS-USB QD Loader
link for windows 32bit
http://www.mediafire.com/file/e8scavjr5xs1cpy/QDLoader_HS-USB_Driver_32bit_Setup.zip
link for windows 64bit
http://www.mediafire.com/file/e8scavjr5xs1cpy/QDLoader_HS-USB_Driver_32bit_Setup.zip
\\ check whether port is ready:
Go to windows device manager.
Look for Qualcomm Driver HS-USB QD Loader 9008 in "Ports COM & LPT"

If yellow exclamation appear, then restart windows with disabled driver signature check.
(repeat step 1 & 2) then check device manager.
This is important to make the phone appear in miflashtool.

3. Install miflashtool
link is updated with newest version (3.3.827.31) as of Aug 2018
http://en.miui.com/thread-345974-1-1.html

4. Install android debug bridge
ADB-Fasboot-And-Driver-v1.4.3.zip, it's just normal install, choose Y for everything.
step by step with picture here:
https://www.foldertips.com/android/install-adb-fastboot-windows-mac-os-linux/

5. Download and extract TWRP to an easy to find folder without space in folder name
TWRP_Patch_MiFlashV3.zip
This will be the first file installed to the phone using miflashtool.
All other files (copied to the phone internal storage) will be installed using TWRP.
Including OS (firmware).
In the future to change OS just copy to internal storage and run TWRP.

Notes:
Use good quality USB wire.
Phone battery at least 50% so it's a good idea to get it fully charged.


Prep Handheld (the phone)
1. Do a factory reset,
delete all files pictures (save what you need to laptop).
Plug it to the laptop.

2. copy following file to internal storage: (Do not extract)
no-verity-opt-encrypt-6.0.zip --> to prevent bootloop
Fix 4G NON UBL
SuperSU-v2.81_201705252021.zip --> optional to gain root access.
if these links broke just google the file name for newer version.
Using these are good enough tho..
Copy your preferred firmware (OS) to internal storage.
I tried this one and it works very well for me:
PixelExperience_ido-8.1.0-20180201-0739-OFFICIAL.zip
This will install basic OREO to Redmi3Pro.

3. Turn off the phone, and go to recovery mode by holding Vol Up and power button.
Choose download, your phone will turn off the screen and in EDL mode (Emergency Download).
Now open the miflashtool.
If Qualcomm HS-USB driver is inslatted correctly,
device should appear in the list.

If nothing appear, repeat step restart windows with driver signature disabled and install Qualcomm driver, then click refresh at miflashtool (red arrow).
Click select and go to the folder where you extract TWRP

Click flash.
Mine got TWRP installed in less than 10 seconds.

Now go to TWRP by holding Vol Up, Vol Down, and Power button.
Red Wolf logo will surprise you.
As I mentioned, everything will be installed here using TWRP.
It is important to first go to "MOUNT" and uncheck  “Mount system partition read-only”.
Then go to INSTALL, select no-verity-opt-encrypt-6.0.zip and swipe to install.
Go to INSTALL, select Fix 4G NON UBL and swipe to install.

Go to INSTALL, select SuperSU-v2.81_201705252021.zip and swipe to install.

To install your new firmware, 

just go to INSTALL and select firmware that you copied to internal storage.

eg.  PixelExperience_ido-8.1.0-20180201-0739-OFFICIAL.zip

Wait approx 20 mins for first boot.
I waited too long and restarted the phone but again it stopped at boot screen (Google logo).
So I go to TWRP (Vol Up, Vol Down, Power), install no-verity-opt-encrypt-6.0.zip,
install PixelExperience_ido-8.1.0-20180201-0739-OFFICIAL.zip,
and Voilla my Redmi3Pro started in OREO in less than 15 seconds.

Glossary:
Root = gain access to root directory
Flash = overwrite Read Only Memory = Installing new firmware
Firmware = OS (Operating System)


Thorough how-to and full credit goes to:
https://www.foldertips.com/android/pasang-twrp-root-ido-tanpa-ubl/
https://www.foldertips.com/android/pixel-experience-stable-ido/
It's just too long for me and too many repeated warnings,
so I made a straight line version for myself in the future here.

Addition:
If your device doesn't show at miflashtool:
Install ADB.Driver.Installer.v2.0; step by step with pictures here:
https://www.foldertips.com/android/install-xiaomi-usb-driver-windows/
Use xiaomi laptop (like me), or borrow from someone and all the xiaomi phone drivers are already preinstalled in its built in Windows10.

I really hope I covered everything and don't lead anyone to bricked phone. Fingers crossed.