Cathay Pacific Asia Miles - Question about upgrade awards with an "on request" segment

I've requested an Asia Miles roundtrip upgrade award for LHR-HKG-SIN return, and so far, all but the HKG-LHR segment have been confirmed. I'd really like to select the seats at least on the one-way portion, particularly on the LHR-HKG segment.

My question has two parts:

(1) If I go ahead and ask the LHR-HKG-SIN segments to be ticketed (for 35,000 miles), will I have to re-request the SIN-HKG-LHR segments, or can it keep the current request code? (I don't know whether keeping the current request code makes a difference.)

(2) If yes to (1), is there a way, in case the HKG-LHR segment is eventually confirmed, that I can have the miles requirement for the SIN-HKG-LHR segments adjusted , given that the difference between 2 one-way upgrades and a return upgrade is 10,000 miles? (That is, if I'm not mis-reading the award charts.)

Bottom line: should I wait for all the segments to clear (and maybe put up with a smaller selection of seats), or should I ticket the one-way segments that are confirmed?

Advanced thanks for any advice and suggestions. :)

(1) If I go ahead and ask the LHR-HKG-SIN segments to be ticketed (for 35,000 miles), will I have to re-request the SIN-HKG-LHR segments, or can it keep the current request code? (I don't know whether keeping the current request code makes a difference.)

LHR-HKG-SIN o/w is 5983 + 1592 = 7575 miles, so a o/w upgrade is 40K miles, return is 70K

AFAIK, if you ticket a one-way upgrade, you can only waitlist on the flights in the segment. i.e. you will need a new booking reference for SIN-HKG-LHR

Correct me if I'm wrong.

Bottom line: should I wait for all the segments to clear (and maybe put up with a smaller selection of seats), or should I ticket the one-way segments that are confirmed?

You could select seats for segments which are confirmed. There is no need to ticket it first. I would wait until, hopefully;) , all segments are confirmed before ticketing.

LHR-HKG-SIN o/w is 5983 + 1592 = 7575 miles, so a o/w upgrade is 40K miles, return is 70K
...
Correct me if I'm wrong.
My mistake :p ; you're right about that.
You could select seats for segments which are confirmed. There is no need to ticket it first. I would wait until, hopefully;) , all segments are confirmed before ticketing.
Will follow your advice, then. :) Thanks! ^

P.S. Just got off the phone with MPC. TerryK, your advice landed me the upper deck exit row window seats (on the confirmed segments). Thanks again!