From Montreal to Hong Kong then Shanghai

I will travel from Montreal to HKG on May.
The day after my arrival to HKG, I have a flight to Shanghai where I stay 3 days, then I come back to HKG.
Then I stay 3 days at HKG.
Then I take a flight to Beijing where I stay 3 days. From Beijing, I come back to Montreal.

Can I use a free-72hour visa to stay at Shanghai ?
Can I use one to stay at Beijing ?

Thank you very much !