Multiple stops within China under seperate bookings and under 24hrs

Hi,
I have flights from London to Xi'an and then following a 3hr stopover I have onward travel to Sydney via Shanghai with a different airline under a seperate booking. My total time in China is under 24hrs.
A) Do I need a visa if I leave the airport at Xi'an to check-in my luggage for onward travel? Does this need to be obtained before leaving the UK or on arrival in Xi'an?
B) If I just take hand luggage and remain within the terminal at Xi'an are there any transit visa requirements?
C) Is the airline from my first booking likely to check baggage through to Sydney even though it is under a seperate booking and different airline?
Thanks for your help!