Is Baiyun Airport open 24 hours? Which rest areas to wait for 1st Metro to Guangzhou south station?

My flight arrive Baiyun Airport at 00.30 AM, can we wait inside Baiyun Airport till 1st metro to GZ south station? In which area? Is airport open 24hours? Can we buy G Trains tiket on the spot to Changsa during low season? Thanks in advance