Mobile Data Providers and Packages

Hi, I am planning to visit China during the end of this month and I have planned to spend 8 days in Beijing and Shanghai and I have few Qs about sim data services in China.a

1. Would I be able to buy a mobile data service sim card from the PEK airport Terminal 2?

2. I will be arriving in PEK T2 at the midnight and would the sim service providers open by that time?

3. What are the available packages?

Looking for help.