Commentaire officiel
1. If you manually fly the aircraft back to the landing things will get out of sync and it may not want to return to the blue dot. Let it land on its own to keep it from getting out of sync. If it does get out of sync you can tap on any corner waypoint while the blue verification line is showing to restart there instead. It is a little weird because you didn't even make it through the first leg of the flight before returning home.
2. See #1.
3. You could save the mission and then run it from there. That way you could unlock the mission if you need to modify it.
4. That version hasn't been widely released yet and is still in testing.