Be aware that the current public releases of Android and iOS mobile are the “New Experience” versions, the same as what you receive in the beta program. Leaving the beta program will not return to the legacy version of the mobile apps.
To leave the beta program, use the same page as when you signed up.
See Join App Betas: Android (mobile), Android TV, Apple TV, iOS and click the Opt In To Beta link. You will be linked to the Google Play store. The page will show if you are in the beta program. If so, it has instructions on how to leave.
