Open Google Play Store
At the top right, tap the profile icon
Tap "Manage apps & devices" and then "Manage"
Find and tap GUI-O application to open its detail page
Rate this app
Open Google Play Store
At the top right, tap the profile icon
Tap "Manage apps & devices" and then "Beta" (or "Manage")
Find the app you want to leave
Tap the app to open its detail page
Under "You’re a beta tester," tap "Leave" and then "Leave"
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