I just booked an itinerary as follows

IAD-ATL-LAX-ICN-NRT-JFK-IAD (all coach)

ATL-LAX is 777 LR on 12/4 I'm PM and booked class is Q. i think it shows about 10 FC seats available on delta.com. Since I haven't used PMUs before, I would like to ask a few questions regarding how to use them.

Q1. Sould I wait till hoping it will clear or should I just go ahead and use 1 PMU to secure the upgrade?

Q2. Can I use my PMU prior to 24 hrs if upgrade doesn't look good?

Q3. Can I use PMU to secure the upgrade and cancell it prior to check in if I could make it without the PMU?

The segment (NRT-JFK) is 777 also but not the lie-flat seats. it is on 12/20

Q4. what's my chance of getting Op-Up?

Thanks and have a good Thanksgiving Holiday!!!