SYDNEY > Hong Kong (layover) > Shanghai > Sydney

Need to urgently visit Shanghai for a family in law funeral.

From what i see the flight into and out of shanghai cant be same so,

Using Qantas Fly to hong kong, then 3.5 hour layover for next flight Hong Kong to Shanghai

Then 3 days later flying Shanghai directly to Sydney again.

Now on website it says need tickets and seat number for flight out but i dont think can get boarding pass until i go to shanghai airport on return flight home? Email itinerary is suitable?