First time to use the Beijing airport for 20 layover time.

My air china ticket is from New York-Beijing-Incheon. I am arriving around 6 pm and leaving for Incheon next day 8 am. My layover time will be about 20 hours. I want to go out side and have a dinner in Beijing and come back to the airport about 11 pm, and will stay at the airport until I leave. I have no idea what the Beijing airport works.

My questions are...
1. Do I need 72 free visa permission? Can I just go out after clearance?
2. To use the airport lounge for resting place, do I have to register or make a reservation first?
3. How long usually take from landing to going outside?

Thank you in advance~