Im currently studying in China and have a Resident Permit.

A good friend of me who is a citizen of one of the Schengen Agreement Countries wants to visit me and also join me for some travel in Asia.

Is it possible to fly Poland - Shanghai(stay couple of days visa free) - Tokio - Shanghai(stay couple of days free) - Bali - Shanghai(stay couple of days free) - Poland?

We want to use Shanghai as transit pub and stay for a few days every time we take another flight, but im not sure how many times you can get a free stay within 4 weeks. Thanks for your help.