Answered by ZUPAN | Dec. 18, 2019 12:43
You are definitely eligible for 24 hour visa free transit both ways and you don't need any kind of visa.
You will print out your flight tickets and have those printouts with you. Also, you will declare at check-in in South Korea that you will travel to Indonesia via Guangzhou using 24 hour visa free transit. After a short inspection of your flight tickets, you will be allowed to board the plane.
Upon arrival in Guangzhou, since you plan to stay at the airport, you will just clear the formalities and you don't need to apply for anything. You will just remain within the transit zone of the airport.
The procedures for your return flights are the same, but everything goes in reverse order.
Also, you will book your accommodation in Guangzhou in advance and have a confirmation of your accommodation booking with you. In reality, if you are flying on China Southern, they are offering a free accommodation to their passengers with layovers longer than 8 hours. You should ask about your option and take that accommodation.
Upon your landing in Guangzhou, you will approach 24 hour visa free transit counter where you will apply for a temporary entry permit and here you will present your flight tickets and also your accommodation confirmation. Since your layover is very long and even more than that, during the night hours, your chances to be allowed to exit the airport are really very good. Anyway, you should have in mind that without an accommodation you will probably not be allowed to exit the airport.