Cruise Departing from Shanghai

I arrive in Shanghai two days before the cruise embarkation on the 30th March 2019. The first port of call is Seoul, South Korea on the 1st April and on the 3rd April we reach Beijing for a two night stop before departing for Jeju Island, South Korea and then onto Japan. We obliviously qualify for a 144 Hours free transit for the UK - Shangha i- South Korea bit; but would we be able to re enter China, Beijing on another 144 hour free transit ie. Seoul - Beijing - Jeju Island? Many thanks.