Need explanation on upload to apple health

Hi All,

New user, I use apple health to track my training and I am trying to work out how and when it uploads workouts to apple health. I assume the following is correct?

  1. When completing a session when running Zwift on an iPhone the main Zwift app will upload to apple health if I have allowed it to do so in apple health?

  2. When completing a session when running Zwift on a Mac or AppleTV or iPad the Zwift companion needs to be also running to upload to apple health?

So… If I am running the main app on an iPad, Mac or Apple TV there will be no apple health upload unless running the companion app?

If I use another hearth rate monitor that is not an apple watch, will the hearth rate be recorded to apple health?

What would happen if the device running the companion app died before the end of the session would I loose the upload to apple health?