Transit at Shanghai Pudong airport for 12 hours

I will be traveling from Seoul , transit at Shanghai Pudong airport , then to Singapore.
Since I have to stay in Shanghai airport for 12 hours before next flight back to Singapore,
1) Can I leave the airport to go for a short sightseeing at downtown?
2) since I transit in Shanghai airport, will my check in luggage at Seoul will send to my final destination Singapore? Or I need to collect my check in luggage from Shanghai airport before I go to downtown ?
I am taking China Eastern Airline.
Thanks