Long Layover in Guangzhou airport. Can Singapore passport holder get out airport?

I am Singaporean who is flying from Singapore to GZ with 5 hrs Layover to LA. Am I allowed to get out of the airport and come back for the next flight to LA?

And how about from LA with 8 hours layover back to Singapore, Am i allowed to get out of the airport too?

I dont need any Visa to China right?