Firstly, you cannot combine a Companion Voucher booking with a partner (or cash) booking. You need to book separately. You cannot combine a cash booking with an avios booking.

Are you trying to book this all using avios, or some as a cash booking?

Question 1
If you have a UK Companion Voucher, you can only use it on a return ticket from London. You can book it as an open jaw, as long as the jaw is less than either flight segment.

You cannot book LHR-BKK-LHR-LAX-LHR with a companion voucher.
You can book LHR-BKK-LHR with a companion voucher.

LHR-BKK, returning LAX-LHR is not valid, as the BKK-LAX 'jaw' is a greater distance than each segment.
LHR-BKK, returning SIN-LHR is valid however, as BKK-SIN is shorter.

As to your multi-city question, you can book LHR-DEL, SIN-SYD, LAX-LHR on one ticket either as cash OR avios award booking. But the cash price is likely to be high, the avios booking would need to be done over the phone, and this could not be paired with a companion voucher.

Question 2
"LAX-LIM,SCL-AKL-SYD-PER,CNS-POM,CGK-SIN,KUL-HKT,RGN-HKG-CMB,DEL-LHR 22,967 mi"

I believe you need to add the surface segment distance between each open jaw, so distance from LIM-SCL, distance PER-CNS, distance POM-CGK, distance SIN-KUL, etc.

And I'm not sure why you are pricing it on ITA Matrix (I guess for comparison?).


I would suggest first trying to work out how to use your companion voucher. Book this first.
Then build a routing around that, and figure out how best to book it. A combination of multi-partner awards or single awards.

Getting the availability to do what you want to do may be very hard.