Upgrading on flights operated by ANA
Each NH/ANA segment requires an unique GPU. A a single GPU can not be used for two ANA segment nor for a connecting UA segment

Summary of Practical Advice from this thread:

* If you have bought a ticket from United (e.g., cause you want PQDs), you likely have UA codeshares of NH-operated flights. However, only NH-ticketed flights can have upgrades requested. When you have these flights, you need to call United (e.g., the 1K desk) and tell them you want to use GPUs on this itinerary. What they will do is modify your ticket so that the codeshares are replaced with the native flight numbers. This takes 10-15 minutes. You will still need to separately request the upgrades using the United GPU request form (link below) for LH/ANA flights.

* The web form will ask for information from your ticket. You will need to enter the NH flight numbers. Also it will ask for your confirmation code and can use the United-issued confirmation code (not the NH confirmation code)

* You should be able to verify in advance whether the upgrade is going to clear based on NH inventory. I class is for Y->J upgrades and O class is for J->F. These are also the business and first 'saver' award buckets, and can be estimated by doing phantom bookings of award travel for the same flights. If saver awards are showing up the classes should be available. Expertflyer and other sites can also show the availability.

* The T&Cs suggest that you cannot request upgrades until 8 weeks before the flight, but various flyertalkers have confirmed upgrades beyond the 8 week window.

* If your upgrade is not confirmed, you can keep trying before the flight.

* There seems to be mixed opinion on whether O and I class inventory is put back into the system as the flight gets closer, but several have reported finding inventory show up 2-3 weeks before the flight.

Below are various T&Cs from United relevant to the applicability of fares, etc, copied from the website.