Nubia Red Magic 3 / 3S Flashing TWRP & Granting Root Access

Detailed guide to Nubia Red Magic 3 / 3S Flashing TWRP & Granting Root Access (Magisk Systemless) Android 9
using Windows 10 computers
UPDATED: Dec. 13, 2020

original thread by Secretcow
https://forum.xda-developers.com/red-magic-3/how-to/guide-flashing-twrp-granting-root-t3936148
https://forum.xda-developers.com/red-magic-3/how-to/guide-unlocking-red-magic-3s-bootloader-t3935630

Requirements:
- Nubia Red Magic 3 / 3S Chinese (CN) ROM
- Windows computer. NOTE: Done this using Windows 10, so I'm not exactly sure if latest ADB works the same on Windows 7.
- Nubia Red Magic 3 / 3S' battery charge should be at 50% above at least.
- You need a USB cable to connect your phone to PC. (Users reported better luck with USB 2.0 port vs usb 3.0.)

NOTE: Done this using Windows 10, so I'm not sure exactly what goes with Windows 7.
=============================================================================
Download latest the ADB (Android Debug Bridge) from Android Developers site.
=============================================================================
1.) Go to https://developer.android.com/studio/releases/platform-tools
2.) Click Download SDK Platform-Tools for Windows.
3.) Click the checkbox beside 'I have read and agree with the above terms and conditions'
and click DOWNLOAD ANDROID SDK PLATFORM-TOOLS FOR WINDOWS
4.) Create a folder in C:\ Drive and name it ADB. Extract platform-tools_rxx.x.x-windows.zip inside ADB folder.
NOTE: platform-tools_rxx.x.x-windows.zip varies per website latest update
5.) Download TWRP from
https://forum.xda-developers.com/red-magic-3/development/recovery-unofficial-twrp-nubia-red-t3962482
or
https://androidfilehost.com/?fid=1899786940962571494

Click Yes on 'Do you want to this app to allow changes to your device.
6.) On your Windows desktop, press the Window logo button on your keyboard, type 'cmd'. Right-click on Command Prompt and click Run as administrator.
7.) On command prompt, type 'cd c:\ADB' and press Enter. *type without quotes *DO NOT CLOSE Command prompt!

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Preparing Nubia Red Magic 3 / 3S
=================================
8.) Enable the Developer Options
Go to your Settings -> About phone tap on the Build Number 7 Times until you see a message “Developer options enabled“
*You can find "Developer options" from Settings > Other system settings menu.
9.) Turn on OEM Unlocking and USB debugging.
10.) Connect your Nubia Red Magic 3 to your Windows 10 computer using USB Cable to a USB 2.0 port.

11.) Go to https://github.com/topjohnwu/Magisk/releases
Download Magisk. NOT Magisk MANAGER

Current version as of Dec. 13, 2020
Stable Magisk Version: v21.1

12.) Get your Nubia Red Magic 3. Swipe down from top, tap on 'Charging this device via USB'. Tap Transmit files
13.) Click on 紅魔3 (or any similar chinese character) and click Browse by path. Copy the Magisk zip you get from Step 11 and paste it there.

14.) Go back to your command prompt (from step 7) type adb devices
This will show List of devices attached <your phone's serial number> device
=============================
Unlocking bootloader
=============================
15.) Type 'adb reboot bootloader' and press Enter. *type without quotes
16.) Type 'fastboot devices' and press Enter. This is to confirm the phone is detected by your computer.
17.) You'll see DEVICE STATE - locked. Unlock it with by typing in the command prompt
'fastboot oem nubia_unlock NUBIA_NX629J'

It will show something like
(bootloader) START update nubia fastboot unlock flag!!!
(bootloader) set state to 1 ok!!!
OKAY [  0.009s]
Finished. Total time: 0.010s

*After executing this step, you'll see DEVICE STATE is unlocked. FASTBOOT UNLOCK COUNT became 1.

18.) Type 'fastboot flashing unlock' and press Enter.
NOTE: If command prompt displays
FAILED (remote: '    Device already : unlocked!')
fastboot: error: Command failed
**THIS IS OK. It means you already done the unlocking before. Only 1 execution of this and no need to repeat again
=============================
Flashing TWRP
=============================
19.) Type fastboot flash recovery twrp-3.3.1-3-NX629J-mauronofrio.img and press enter
It will show something like

Sending 'recovery' (98304 KB)                      OKAY [  2.306s]
Writing 'recovery'                                 OKAY [  0.639s]
Finished. Total time: 2.961s

20.) Get your phone. You can unplug it from the USB cable. Boot to the newly flashed TWRP recovery. Press Volume down, make sure the blue area above says 'Reboot to recovery mode' press power button to confirm.

* After reboot, 'The boot loader is unlocked..' warning will show - THIS IS NORMAL
afterwards, if you are following the steps well,
'teamwin recovery project' logo should show. Wait for it to finish loading.

After this, TWRP will ask for your Password. (Mount Decrypt Data)
toggle ABC key to change the keypad to numbers. key in your PIN and then tap the blue checkmark button.
=============================================================
Unmodified System Partion will show - ONE TIME QUESTION ONLY
Keep System Read only? Question and an explanation
just "Swipe to Allow Modifications"
=============================================================

=============================
Installing Magisk
=============================
21.) Tap 'Install'. Search for Magisk-v2x.x.zip. Tap Magisk-v20.3.zip and 'swipe to confirm flash'.
22.) After finished, tap 'Reboot System'.
23.) Go to https://github.com/topjohnwu/Magisk/releases/
	 Download the latest Magisk Manager. MagiskManager-v7.5.1.apk (as of Jan. 23, 2020)
     Install it on your Nubia Red Magic 3.
	 After installed open Magisk Manager to confirm the version and manager installed.
=============================
Installing GApps
=============================
24.) For the meantime, download open_gapps-arm64-9.0-pico-20200117.zip (Jan. 17, 2020)
https://sourceforge.net/projects/opengapps/files/arm64/20200117/open_gapps-arm64-9.0-pico-20200117.zip/download
*Thanks to Jay Bag'z for finding out the latest GApps have issues with NRM3 v2.45 update.

25.) Same as step 13, this time copy and paste open_gapps-arm64-9.0-pico-2019xxxx.zip there. 'xxxx; here depends on the date of gapps version.
26.) Go back to command prompt and type 'adb reboot bootloader' and press Enter.
27.) Press Volume down, make sure the blue area above says 'Reboot to recovery mode' press power button to confirm.
It will boot to TWRP asking for your Password. (Mount Decrypt Data). Type your PIN that you set on your phone
28.) Tap 'Install'. Search for open_apps-arm64-9.0-pico-2019xxxx.zip. Tap it and 'swipe to confirm flash'.
29.) After finished, tap 'Wipe Cache/Dalvik'. Swipe to Wipe.
30.) Tap 'Reboot System'.

Afterwards it will show the bootloader warning and will boot into Android.
Congrats your NRM3 is now granted with root access and GApps is installed