Hello,
the moodlemobile2 repository you mention is the one used for development. It contains the code for the next release and it needs to be built using gulp in order to make it work.
We have another repository used for publishing the apps: moodlemobile-phonegapbuild. This repository contains the code of the last release of the app, and it's already built in the build files.
You can find more information in here.
The version 3.2.0 of the app will work fine with Moodle 3.2. Moodle Mobile 3.2.0 will still work with older versions of Moodle, but you might lack some of the new features. Also, older versions of the app work with Moodle 3.2, but in this case you'll also lack the latest features of the app. So in order to have the maximum number of features we suggest to use the latest version of the app and Moodle.
Kind regards,
Dani