How to force an Android app to stop updating to a beta version automatically without asking?

Question

Android

Device given:

• Smartphone "Meizu 16th" (M882H), 8/128.
  
• Firmware latest stable: Flyme 7.3.0.0 RU (Android 8.1.0).
  

For a long time I used "Wanderlist", but in connection with its closure, I switched to Microsoft To-Do, importing the base from WL. On the desktop, the application works as expected, but on my smartphone model, it works in a completely sudden and unexpected way.

0.1. Auto-update apps are disabled in the Play Store .
0.2. In the Microsoft To-Do app itself, the option to participate in beta testing is disabled .
1. If you download this application [namely on the device of my model], after a while it itself, absolutely without demand or warning, is updated to "To-Do β", and it definitely does not start by tap.
2. Removing and reinstalling saves a maximum of a couple of hours. Then, without options, the undesirable action from point 1 will happen.
3. Even if you delete the application from your smartphone, then if there is Internet, it will inexplicably download and install without demand, and it will immediately be the same beta that does not start.

Judging by the reviews in the Store, the problem occurs only on the "Meizu 16th" device (I have not seen such bug reports from users of other smartphones).

There is no other official firmware (more recent) for this phone yet.

I wrote to MS in support, they say - Play Store is to blame, not us. Wrote in support of the Play Store - they say we just place apps from different manufacturers, it's not our fault, please contact the company that released the application. In general, a vicious circle.

Actually, I would like to understand:
1) why this incorrect behavior, described above, occurs,
2) how it can be corrected.

Please DO NOT offer:
- change smartphone
- change firmware to custom, etc.
- change the very stuffy application.

Thank you.