Whether I will be able to apply for the 72 Hour Transit.

I am an Australian passport holder travelling from Moscow in September 2016 on a Air China flight and will be arriving in Beijing Airport on 25th September.
I will be connecting with a Singapore Airlines flight on 29th September for return to Australia via Singapore.
Please confirm:
Whether I will be able to apply for the 72 Hour Transit visa.
Will I be able to take any tours whilst in transit, specifically the Great Wall at Mutianyu.