Leaving from a different airport, 72 hours free transit in Shanghai

Hello! I have an Air Canada plane ticket that will be flying from Canada and landing in Shanghai. I am in the process of purchasing a second ticket onward to Taiwan because that is my next destination. May I utilize the 72 hour visa for staying in Shanghai for the three days before departing to Taiwan- furthermore, may I book my plane ticket to Taiwan but leaving from Hong Kong airport and use the 72 hours to travel down to Taiwan before leaving China?