There are several achievements for completing each Act in less than an hour ("No Time to Rest", "Sandskimmer", "Swift Descent", "On the Wings of Angels", "In a Hurry?"). Can I do these runs on normal with a character who has already completed each Act? Do I need to do the runs with a character who has never been to the Act in that difficulty? Does the timer start when I enter the Act the first time, and does it mark an hour from that point, or only count one hour of gameplay time? How do these speed run timers work?