Alpha / Beta testing
Recommended only if you have multiple devices (one running the stable version, while testing the development version on the other one).
When becoming a tester you will be getting alpha / beta / stable versions in that order on all devices on which signed-in with the same Google account, but you can disable automatic updates on the main device and that way you control when you install a version, after testing it on the other device first.
Support / Feature requests
Create a ticket using the link below, following the general guideliness please.