[Huawei Mediapad M3 Guides, News, & Discussion] aBikeLife:
I had to do a lot of link-hopping, searching, and plain ol' trial and error to get this done, so I thought I'd share my steps specifcially for the BTV-W09 wifi (US). I've given credit to the appropriate sources for each step of the process.

STEP 1: Downgrade MediaPad M3 to Marshmallow (from How to Downgrade MediaPad M3 from Nougat to Marshmallow)

From my experience this is just the simplest way to get the bootloader code to LOCK/UNLOCK the bootloader.

Requirements:

1.	Download MediaPad M3 Nougat Rollback package – Rollback file will change Your software info to C900B300. As far as I know, this is a specific firmware key, that allows to fully update the firmware to any other version.

MediaPad M3 Rollback Package For BTV-W09 C100 (EU): https://goo.gl/SKTj7D

(http://download-c1.huawei.com/download/downloadCenter?downloadId=94469&version=380487&siteCode=it)

2.	Download MediaPad M3 full OTA Software File – This file will switching back your MediaPad M3 to Marshmallow.

MediaPad M3 Marshmallow Firmware BTV-W09C100B006: https://goo.gl/8tXFK7

(http://download-c1.huawei.com/download/downloadCenter?downloadId=94471&version=380540&siteCode=it)

How to Downgrade MediaPad M3 from Nougat to Marshmallow

1.	First, download Android Nougat Rollback Package for MediaPad M3 from above and extract it.

2.	Now create a folder dload in the root of your SD card and place the update.app file in that folder.

3.	Now turn off your device.

4.	Now press “Volume Up + Volume Down and Power Button” together. The update process will start automatically.

5.	Now wait for some time to complete the process. Your firmware version should now be on “B300”.

6.	Now download the full Marshmallow firmware from above and extract it.

7.	Now move the update.app file in SD card folder (Replace the rollback update.app file).

8.	Now again press “Volume Up + Volume Down and Power Button” together to Downgrade MediaPad M3 from Android Nougat to Android Marshmallow

9.	Done.

STEP 2: Unlock Bootloader (from here and How to Unlock Bootloader of Huawei Devices)

* Use the Chinese language of the Huawei page to get the unlock code because the Captcha function on the English page does not work. Use the English and Chinese pages next to each other so you know which button to press.

1.	First, enable ‘USB debugging’ and ‘OEM Unlock’ option from setting>developer option>. To enable Developer Options, go to About phone and tap the Build Number 7 times.

2.	Install the ADB and fastboot driver for windows or ADB and Fastboot for Mac and then restart if you already have the driver installed then skip this step.

3.	Now create a Huawei id from this page.

4.	After creating a Huawei id, fill out the detail on this page.

5.	It will ask for a Product ID code, (open your calculator and enter ()()1357946()()=. An 8-digit ID will appear.) fill the MEI code and submit.

6.	Now you have unlock code. Save it for later use.

7.	Now go to ADB and Fastboot installation directory open ADB folder and open the command window there by pressing and hold the ‘shift’ key and right-clicked anywhere in that folder.

8.	Now connect your phone to PC and reboot the device into fastboot mode by typing “adb reboot bootloader”.

9.	Type “fastboot devices” in command prompt and hit enter, it gives you serial numbers in return means your phone connect properly.

10.	To unlock bootloader of BTV-W09, type “fastboot oem unlock XXXXXXXXXXXXXX”. Here replace unlock key with the key you got. For example “fastboot oem unlock 21084949302847”.

11.	Above step will Unlock Bootloader of Huawei Devices. To restart the system type “fastboot reboot”.

12.	SAVE the product number and unlock code for future use. The unlock code will continue to work even after upgrade to EMUI5.

STEP3: Install TWRP Recovery (from TWRP greatslon mod)

1.	Unlock bootloader (see STEP 2 above)

2.	Download and unzip this archive: https://goo.gl/16o8cX

(https://cloud.mail.ru/public/56Yv/D9nDBW39V)

3.	In command prompt:

adb reboot-bootloader

fastboot flash recovery twrp.img

fastboot reboot

STEP 4: Ugrade to EMUI 5 (from Huawei Mediapad M3 BTV-W09 Nougat B350 EMUI5(USA))

1.	Download MediaPad M3 B350 Nougat update.zip for USA BTV-W09C128B350

Update.zip https://goo.gl/iD2sr3

(http://update.hicloud.com:8180/TDS/data/files/p3/s15/G1224/g490/v88572/f1/full/update.zip)

2.	Download update_data_full_hw_xx.zip for MediaPad M3 from above and extract it.

Update_data_full_hw_usa.zip https://goo.gl/TSKqpW

(http://update.hicloud.com:8180/TDS/...72/f1/full/hw/usa/update_data_full_hw_usa.zip

3.	Reboot to twrp (volume up + power)

4.	In TWRP tap on install and select update.zip file 1st, then swipe to install, Don’t reboot.

5.	Go back to main menu and again tap on install and select “update_data_full_hw_usa.zip” file, and again swipe to install it.

6.	Now reboot & Nougat will be running on your device.

STEP 5: ROOT

1.	Unlock bootloader again if needed (see STEP 2 above)

2.	Download twrp_BTV-W09_5_greatslon.img: https://goo.gl/ijUd6U

(https://androidfilehost.com/?fid=817550096634750328)

3.	In command prompt:

adb reboot-bootloader

fastboot flash recovery twrp_BTV-W09_5_greatslon.img

fastboot reboot

4.	Download SuperSU-v2.82-EMUI5-SELEnforcing.zip https://goo.gl/mPfUBf

(https://www.androidfilehost.com/?fid=673368273298961353)

5.	Reboot to TWRP Recovery

6.	Select Install and select SuperSU-v2.82-EMUI5-SELEnforcing.zip from download location

7.	Reboot to System

STEP 6: RE-ENALBE 5GHZ WIFI RADIO (from Any way to unlock the 5GHz WiFi band for US-version? Thanks feretio!)

1.	Using a root file explorer (e.g. Root Explorer) open cust_spec\vendor\etc\cfg_btv_hisi.ini

2.	Change the value of band_5g_enable from 0 to 1:

band_5g_enable=1

3.	Save and reboot

Now you're truly done done!