Hello, I have plans to travel to China in late January and February, I have not booked tickets

and want to know if it is possible to go to the station and then buy one or two days in advance.

A. I'll have trouble finding tickets for one day to another?
B. seats are finished in that time when I want to travel?
C. I can buy tickets for 2-6 hr before it comes out?
D. will be difficult book with 1 or 2 days in advance?

My itinerary is flexible i will go like backpacker. And very variant depending on weather conditions and I intend to do outdoor activities.

Will thanks for the info