Gen3 flow meter: leak detected in vegetable garden?

BTW, I read the materials released here and here prior to posting but they didn’t answer my questions.

For example:

Is leak detection only active when a zone is watering? I have a few spray heads with older non-pressure regulated bodies that trickle leak even when the zone is off. Would the flow meter be able to alert me to how much water is lost?

Specs say it only measures down to 0.5GPM but this conflicts with this statement:

“The flow meter detects broken heads, ruptured pipes, and even low-flow leaks with highly-sensitive, state-of-the-art Vortex technology…”

Also, what if I don’t have a backflow preventer? We use reclaimed water - if one is installed I can’t see it - everything is below ground.