USA to NZ with Gangzhou Layover

Hello! I will be traveling to New Zealand with a layover of 9 hours in Gangzhou on the first flight, with a 20 hour layover on the return flight. Will a 24-hour without Visa be applicable for both layovers?

What will be required? Do we need proof of a hotel reservation in China if we wish to leave the airport? Are there any requirements for the passport? (Example: Needs to be six months away from expiration, etc)

Thank you!