If flying from Melbourne to Dubai via beijing and want to spend less than 72 hours in beijing on

If flying from Melbourne to Dubai via beijing and want to spend less than 72 hours in beijing on an Australian passport, can I qualify for 72 hours transit permit. In such a case, I have ticket from Melbourne to Beijing and Beijing to Dubai or a separate airline.

Also if doing this event in reverse way, like from Dubai to Melbourne via Beijing. Main purpose is visiting Bejing for 2 to 3 days visiting Great Wall and Forbidden city.