[Huawei P9 Plus Guides, News, & Discussion] Tecalote:
Restore Firmware - downgrade to Nougat - rebrand back

Restore current firmware (if you are on EMUI or OpenKirin ROM) → check out following Post:

https://xdaforums.com/showpost.php?p=77905152&postcount=833

How to go back from Oreo to Nougat → and rebrand back​

A) Method by using HiSuite (on PC):

1) If you have Magisk Root - uninstall Magisk with Magisk Manager (Button Uninstall)

2) Make sure, you have EMUI-Stock-Recovery installed (it does not work with TWRP)

3) Download Huawei HiSuite: https://consumer.huawei.com/minisite/HiSuite_en/

4) Update HiSuite on PC to (minimum) version: 8.0.1.302_OVE and connect your Phone with PC and HiSuite.

5) Let HiSuite install HiSuite App on your Phone - accept the Permission requests. Once that is done:

6) Click on "Systemupdate" - a new window pop up and show you your current version, click on the Link "Change version" - then you can downgrade to the latest Android 7 AL10 firmware

7) → then it is possible to use HWOTA7 again for rebranding back...

B) Method by using HuRUpdater → requires external SD or USB OTG:

If you want to go back from unofficial Oreo to Nougat and rebrand back to your original brand, you can do it with simply steps.

→ Note: HuRUpdater can not only be used for Downgrade, it can also be used for Update Firmware - It depends only on which firmware you pack together with HuRUpdater in the folder (which you have created on external SD or USB OTG)

→ The Firmware must be FullOTA-MF (same renaming than with HWOTA7 Tool)

1) Bootloader must be open

2) Flash TWRP for Oreo Download TWRP by Pretoriano80: https://www.androidfilehost.com/?fid=1322778262903998750

3) Backup your data with Huawei Backup (because TWRP can not acces data for now, because it has no encryption/decryption support)

4) Make a folder on your external SD and name it: Downgrade or Update (or however) ;)

5) Copy the 3 Firmware zip files into the folder and make sure, two zip files are renamed (same as you did for HWOTA7)

6) Download HuRUpdater_0.4.zip from here:http://www.mediafire.com/file/r14sor2g4cbugzw/HuRUpdater_0.4.zip

7) Copy HuRUpdater into the same folder together with the firmware zip files. If you have the Nougat AL10 zip files inside, you will downgrade.

The folder contains now 4 files:

HuRUpdater_04.zip

update.zip

update_all_hw.zip

update_data_public.zip

8) Boot into TWRP. It will ask you for password. Just cancle. In TWRP open "Wipe" - but dont wipe anything - you must use the Button on the right Format Data. Confirm with typing: yes. Soon data is formatted, go back to the main menu and open Reboot - but do not reboot System - you must Reboot Recovery

→ Note: Format data is only important until we have TWRP with working data decryption

9) After TWRP is rebooted go "Install".

10) Navigate to the folder which containes the files and flash ONLY HuRUpdater_04.zip In some seconds the Akku vibrates - in this moment press for one second the VOL- Button. Now HuRUpdater will flash automatically the FullOTA-MF Firmware.

11) Once it is done, use on the left: Wipe Cache Button. After go back to the main menu and Reboot RECOVERY.

12) Your device has rebooted now into EMUI Stock Recovery. From there perform Wipe Cache Partition and Factory reset and boot to system.

Once you are back to Nougat - you can use again the HWOTA7 Tool to rebrand back to your original brand. Just use Change location (for your original cust) and make sure, the Firmware is in the update folder..

Credits:

[MENTION=3975929]zxz0O0[/MENTION] Many thanks for HuRUpdater :)

HuRUpdater Thread: https://xdaforums.com/honor-9/development/tool-flash-official-firmware-recovery-t3769279