Could I get my tickets in Hong Kong?

Helloo.
I will arrive to Hong Kong on 11th July. After several days, I want to go by train:
15th July Shenzen - Guilin
Tongren - Chengdu
Chengdu - Leshan - Chengdu
Chengdu - Xian
Xian - Pingyao
Pingyao - Beijing
29th July Beijing - Shanghai

Then, could I buy all of them at the same time?
Could I have them in my hotel in Hong Kong before my departure to Guilin?
Thanks.