Australian and American in Saudi Arabia, traveling to China

Hello, I am Australian and my wife is American. We are both residents in Saudi Arabia, and we want to visit China for tourism and to see my sister (Australian) who is currently living there in Shanghai.

Do we need to travel to Riyadh and submit our Application form (L type)?

Can we fly into Lhasa (Tibet) from Nepal? (We have a tour guide booking a tour for us in Tibet)

Thank you!

Chris