Flight GuangZhou to HongKong

Hello! I would like to fly from Guangzhou (travel there from Europe) to HongKong. Do I need the visa if I do have the ticked purchused before but it is not connection flight- HK flight is seperately from the GuangZhou flight, still happening some hours after arriving GuangZhou airport. I am also not planning to go out from airport. But what about checking in to HK flight- can I use 24h free permit? where to apply for it?