What to do if I have 9 hrs before my transiting flight

Hi, I am going to fly from Korea to Baiyun and have 9 hrs to go before I board the transiting flight back to Singapore. Kindly advise the procedures. Can I request my leave my luggage with the airline for them to transfer to the next flight I am going to board? If not, will I be able to leave the luggage at the airport? Was told that I will be allowed to get out of the airport and return again for my flight as long as my transiting hours is at least 4 hours. Is it true? Appreciate your help!