Hi! I have a valid Chinese visa in my Canadian passport, but I recently had to renew my passport before the Visa expired. Is the visa in my Old passport still valid, or do I need to apply for another visa in my New passport?

Regarding to reply to Mr Sade from Israel: "If your stopover in Beijing airport is less than 24 hours and you don't leave the airport, a visa is not required."

Does the same apply to the Shenzhen airport? i.e. If i wish to fly from Hanoi, Vietnam to Shenzhen and then take a shuttle bus directly to Hong Kong from the airport, do I still need a Chinese visa?

Thank you!