Avios multi-carrier booking – add sectors later?

[Fraser]

Apologies if already answered elsewhere but I couldn’t find the answer.

I am looking to do a multi-carrier Avios booking to Asia and possibly Australia. Do I need to book all sectors (up to 8?) at once, or can I book the initial outbound as a starting point then add to it? What about the outbound and return, but then add a further side trip in-between (eg out to Phuket on Qatar, on to KL, back to UK but then add a KL to Seoul return before the return later?

Also wondering if there is any restriction on Qatar different levels of reward seats, eh if I can see it on their website, can it always be added to such a multi carrier booking?

[BA Flyer IHG Stayer]

To be on the same booking it needs to be done at the same time.

You can only book flights that are available via BA.