(1) clock starts at first part of the flight
(2) Not needed
(3) I did, it is very fast, 15 min line, no booking needed, and turn around time is 3-4 hours to get results. But you have to go to the airport the day before your flight, as your do not want to arrive 6 hours in advance just to do the testing. I am shocked the US testing requirement has not dropped, there is no point in testing anymore