Can you listen to users' conversations through Micro Guard Android? Can you access phone calls or conversations in any way?

No, we cannot! Please excuse the misleading information shown by an Android system message:

When an app protects (blocks) the internal microphone of an Android device, Android displays a system message saying that the app is “recording” through the microphone.

Of course, Micro Guard does not record you or your conversations—it protects you from exactly that.

The app does not require internet access to work, so from a technical standpoint it is not possible to intercept conversations.