Can I purchase a round trip train ticket from Guangzhou East Train station to Hong Kong?

Yes, you can buy the return train tickets at the train station. It costs 190HKD per person. If you buy at GZ, you need to pay with Chinese Yuan (CNY). The last train from HK to GZ leaves Hung Hom around 20:01.

Thanks Vivian.

Can I bring my Australian GPS in China for travelling purpose? Will I be detained in customs if I did?

Thanks,
Daffodil

You will not be detained, but you need to declare your device at the custome.
I should remind you that you need to download a suitable map for traveling in China.

Thanks for the advise Lily, will do that. I want to go to Lantau Island to see the Big Buddha but I'm scared of riding the cable car in Ngong Ping.....is there another way to get to Ngong Ping 360 from Hung Hom Train station? Many thanks for your time, I really appreciate it. Daffodil