Legend Run

Ascoop24

I am thinking of attempting my first legend run next month and am curious on a few keep points.
1. Is it just heroic and master? Or is it all four modes?
2. If I'm not on as soon as it drops am I losing time? Example that it comes live at 12pm but I don't get on until 1pm. And I finish it at say 4pm. Will my time be 3 hours or 4 hours?
3. Final question does the timer start as soon as I open up the quest? The app?
Thank you for reading and your comments. Just making sure I do this right.

Sungj

1. It is just heroic and master
2. No the time the event drops doesn't effect your timer
3. The timer starts when you begin the heroic event

Good luck!