Does the Guardian feature stop when using Sport mode?

Yes, the Guardian feature is suspended during exercise. 

During exercise you often intentionally exceed your normal health metrics, like heart rate and breath rate. At such times, visible and audible Guardian alerts are undesirable. To prevent these interruptions, Helo has updated Guardian programming so that when you start a sport activity, these alerts are suspended (except for fall detection).

What is the QR code feature on the App, and what can I do with it?