guguIf you installed the stable release, you are only prompted to update to new stable releases; if you installed the beta, you are only prompted to update to new betas. Each app stays on its own update channel.
Why they can coexist
On your system they are two separate apps to begin with, each with its own data. So the two can be installed side by side on the same machine — installing the beta doesn't affect the stable release you are using. The same goes for phones.
Which platforms have a beta
The beta is available on Windows, macOS, and Android — whoever is helping test on a platform should be able to get the beta for that platform.
A beta shipped at the same time is the same code with the same version number on every platform. If two platforms report different version numbers, something is wrong; that is not normal.