From Australia to russia with a layover in Guangzhou Airport. Am i eligible for 24h visa ?

As an Australian citizen you can be eligible for both 24 and 144 hour visa free transit. Kristina, please, use correct terminology because this is not 24 hour visa, but 24 hour visa free transit, so you do not need any kind of visa at all. So, if your layover is shorter than 24 hours, you will be covered by 24 hour visa free transit and if your layover is longer than 24 hours, you will be eligible for 144 hour visa free transit. In both cases you do not need any kind of visa.

If your layover is longer than, roughly, 8 hours, you could probably be interested to leave the airport and to explore the area or to have a night rest in the hotel if your layover is during the night hours. In that case, the first thing you will do upon your landing in Guangzhou is to approach 24/144 hour visa free transit counter where you will apply for a temporary entry permit for free. There you will present your flight tickets as well as your hotel booking confirmation if you have one. After a short check, you will be granted a permit and you will continue toward the immigration to exit the airport.