[Asus ZenWatch 3] csrow:
Going from V 2.0 down to V 1.5 custom ROM with OTA disabled

I have been going back and forth between V 2.0 to V 1.5 few times. Every time I downgrade to 1.5, OTA will push the watch back up to 2.0.

So, finally I used the method [MENTION=4438613]nmdang[/MENTION] suggested to disable the Update Service and that seems have worked. So I am documenting the steps I took to downgrade to 1.5 and lock down the OTA.

This guide assumes you have a working knowledge of ADB, Fastboot, and TWRP and your computer is set up properly to communicate with the watch and the watch has the ADB debug enabled.

If you are not comfortable with ADB, Fastboot, TWRP, or rooting, do not try these steps.

Your warranty will be voided and you may brick your watch.

By the way, all the data and apps will be lost during this procedure so make sure you have a way to recover.

Here are the files you need;

1) grab the boot.img from inside stock MWG68 ROM from this page. System and recovery image is not needed.

2) Latest TWRP recovery image from this page

3) V 1.5 custom ROM from this page

Steps;

- Make sure you have a working communication link in ADB and Fastboot by running the devices command to check each time as you change the mode.

1) adb reboot bootloader

2) fastboot oem unlock

(at this point you need to push the side button for a couple of seconds to accept the unlock)(this step will erase all the data)(wait for the watch to get back into bootloader mode)

3) fastboot flash boot boot.img

(flash the v1.5 stock boot image since the v 2.0 boot image will not work with a V 1.5 ROM)

4) fastboot boot twrp_whatever_you_have_named_it.img

(this will start the TWRP recovery and you'll be back in the ADB mode)

5) adb push -p custom_rom_whatever_you_named_it.zip /sdcard/

- now work from your watch in TWRP mode but leave the watch still in the stand. At the start of TWRP, allow for system modification.

6) mount system

7) wipe - system, data, dalvik cache, cache

8) install zip custom_rom_whatever_you_named_it.zip

9)reboot system (do not allow TWRP to be installed)

- the watch will reboot with a warning message about the unlock bootloader. Do not push the button and just wait for it to start. It will take some time.

- You should see the large ANDROID boot screen graphics instead of the google version if the ROM has been installed correctly. The first boot will take long one.

- As soon as watch goes past the link with the phone process, watch will ask the permission to debug. Select [Always allow]

- as the watch starts syncing, the ADB should be enabled.

10) adb shell

11) su

12) pm disable com.google.android.gms/.update.SystemUpdateService

13) pm disable com.google.android.gsf/.update.SystemUpdateService

14) exit

15) exit

That's it. Now you should have a custom V1.5 ROM on your watch with OTA blocked.

Once you are happy everything is working, optionally, you can go back and lock the bootloader to remove the warning message and speed up the boot up process.

EDIT:

I'm adding one more step in order to block notifications coming from the phone.

16) On your phone go to settings / notifications and find Google Play Services. Turn off all notifications (set it to level 0) for Google Play Services.

End of EDIT: