Is there a good primer somewhere on how to book strange routings / layovers? Eg. what is actually allowed, and how to go about booking it?

I want to book:
Outbound: ORD-AUS(overnight layover<24 hours)-HKG
Return: HKG-NRT(overnight layover <24 hours)-ORD

Is this even possible? If so how would I go about trying to book it? I called an agent and the first one I tried said it was not possible to book an AUS layover from ORD to HKG, and said it needed to be essentially a separate one-way fare.

Gravy would be booking it in W if GPU space is available (fat chance I know).

Thanks