Refugee with US travel document - 16 hour stopover in Shanghai Pu Dong on the way to Cambodia

Hi!

I'm citizen of Belarus, but have asylum in US and travel as a green card holder with US refugee travel document. I want to fly to Cambodia and get VOA. All the flights are through China, in particular Shanghai Pu Dong, i.e. route looks like Los Angeles - Shanghai (12 to 16 hour layover) - Cambodia.

1. Do I need transit G to China or 24-hour rule will apply to me? Border control often gets confused when they see refugee travel document instead of a passport.
2. I want to get visa to Cambodia on arrival, at the airport, so while transiting through China, I will only have flight tickets but no visa for my final destination. Will that be a problem?

Thank you!