Please accept my apologies for asking what may be naïve questions, but a search of the forum and FAQ didn’t turn up clear answers.

I am looking to book a LONE4 RTW fare (with a complicated 16-segment itinerary). For the first flight, SYD-HKG, there is currently no viable choice other than using CX metal. But for both mileage accrual and customer service reasons, I would much prefer to book that under the AY codeshare flight number, and have the ticket issued by AY. The AY chat agent indicated that they can’t do that, that they can only handle ticketing if they operate the first flight, and the ticket must be issued by that first operating carrier. But that doesn’t really make any sense, because if that were the case, why would AY even publish fares for a LONE4 ticket ex Australia, when they have never operated to Australia at all?

Do you have any suggestions as to a way around this, and/or know of a good booking site which might allow me to construct this itinerary using the codeshare flights? I know that agents can do that manually, since I have done that in the past. But then have to deal with the agent’s limited hours and imposed service fees for flight changes. And the OneWorld tool doesn't ever seem to show any of the codeshares, even when ExpertFlyer does show them, and with L class availability.

Also, the OneWorld booking tool is acting like the following itinerary is not legal, having too many segments in Europe/Middle East. But I think I am counting them up and it is correct:

HKG-HEL
HEL-LPA
LPA-EUN
EUN-CMN-BCN
BCN-MIA

I see four flights within Europe/ME and stopovers in four cities in Europe/ME. What am I missing here?

Finally, does the ‘preferred airline’ box of the booking tool actually affect anything? It didn’t seem to in my experience.

Thanks for your thoughts.