Do we have to apply for Transit Visa?

My wife and I are traveling from Delhi to Manila on 2nd June and returning on 14th June, by China Southern Airlines, with change of plane at Guangzhou Airport, both, while going and coming back. Please advise if
1. It is required even if we stay within the airport?
2. If it is required, then 1 application with multiple entry or 2 separate applications are needed separately for the outgoing and return journeys?