HK-Shenzhen-Huangshan train ticket pickup

I want to go from Hong Kong to Huangshan return. I understand I have to first go to Shenzhen and then take another train to Huangshan.
1. Can I pick up both my HK to Shenzhen and Shenzhen to Huangshan tickets 1-2 days before departure at the Hong Kong West Kowloon station?
2. Can I also pick up my return leg while I'm in HK?
3. How much time should I allow to transfer trains in Shenzhen?
thanks