Pretty sure they were asking if you could still access all the functionality currently provided by the app if it were to go away for some reason (who can see the future? It's not impossible Mitsubishi goes out of business or the app gets cancelled/pulled after some number of years)

If you lost your phone, would you still be able to manage the heat pump through other interfaces?

If the app wasn't updated for ${latest phone OS}, would you be be unable to upgrade the phone OS?