Connecting Flights with Layovers.

I understand the basics that you can't arrive to china and depart back to the same destination for this to work. However, what if that city is not your home destination, nor your country of your passport? For example, I'm planning to fly JFK-HEL-PVG (there is a short layover in HEL, but I don't plan to leave the airport). On my return, I have PVG-HEL-JFK however there is a 24 hour layover in Helsinki where I plan to visit the country and leave the airport. Does this trip qualify since I will spending time in Finland on the return? Or since the itineraries are the same, it won't work? If that won't work, can I go spend a day in Hong Kong or Taiwan and then fly back through Shanghai on my way home? Thanks for the help!