I have a OW award tix for travel next month where we are going SYD-MEL-NRT-LAX-BOS, with short stopovers in MEL and LAX, and a 23 hour stopover in NRT. My understanding is that it counts as SYD-BOS great circle distance in terms of mileage. In fact I attempted at one point to move the MEL flight a day later, and it caused the mileage required to jump!

The 24 hour rule certainly applies if you have no other option to get out sooner. I'm not sure if it is legal if there is a possible connection within 4hrs. See the FAQ sticky.