Can I travel with tickets from different airlines?

I from Switzerland and I am studying in Seoul, South Korea. Now I would like to visit my friend in Hong Kong. On the way back to Seoul, I would like to make a stop at Beijing for 2-3 days. Is it therefore possible, to use the 72h visa exception rule if my flight is as follows: Seoul - Hong Kong (direct flight). Hong Kong - Beijing - Seoul. However, these two flights would be booked with different airlines! is that possible? Thank you!!