72 hours

Hi.. me and my friend are flying together to Shanghai PuDong with Etihad Airways from Europe, so on my initerary is onward flight from Abu Dhabi to Shanghai and return is Seoul to Abu Dhabi (multi-city initerary - arriving in Shanghai and then returning from Korea). We want to stay in Shanghai for 55 hours and 45 minutes and then we are flying with Spring Airlines to Hong Kong. Do we need to apply for a regular visa or we could use these transit conditions? It is not problem that our final destination on Etihad ticket is Shanghai and then we will use another Airline to fly to Hong Kong? It is not layover (like on way Rome - Shanghai - Sydney via China Eastern). Thanks!