I have a very long layover in Guangzhou, and I was looking forward to heading down to Hong Kong, before having to head back up to the airport in China. I am an Australian citizen, and I know there is a (72?) hour visa free period for me since I am transiting. However, this brings into the question of going to Hong Kong. Do I need a multi-entry visa for China or can I re-enter at the land border with the visa free period? Thanks!