travel by subway or taxi in HK and Guangzhou

Hi, next month I will arrive at GZ East Station fr HK before proceed my journey to Hanoi via Nanning by train.

1) Can I buy train ticket at GZ East Station for train no 2571, depart from GZ main station 4.52pm. If yes, which counter n what time is counter operate.

2) Which way is faster n cheaper from GZ East to Lido Hotel, Beijing Road. By Taxi or metro?

3) Which way is faster n cheaper from Lido Hotel to GZ Main Station. By taxi or Metro?