eta GZ airport about 5:30pm, want to go to HK

my flight eta GZ airport about 5:30pm.
I like to know if I can get on the train from Guangzhou East Rail Station to HK.

1) How long will it take to get to the East Rail Station from the airport ?
including luggage pickup, immigration at airport to getting on the metro line

2) is there just one stop on Metro line (from airport) at the East Rail Station ?
If more than one stop, please advise which stop to get off ?

3) how long it will take to purchase tickets at East Rail Station ?

4) can I buy the tickets the same day, ie: right after arriving at the East Rail Station, and board the next ride to HK ?

your advice greately appreciated. Thanks.. YL