Three Chinese layovers

We are traveling from Ho Chi Minh City to Nanning to Chengdu to Hangzhou to Los Angeles. The layover in Nanning is 17 hours and we want to leave the airport. However since we have two other stops in China it is more than 24 hours before we leave the country. We dont want to leave the airports at Chengdu or Hangzhou. Are we eligible for any free transit policy?