Hello, could I get a 72h visa if I buy a one way ticket to Beijing and a second one leaving BJ?

It depends where you arrive from and leave to.

Each airplane ticket must include *** 3 *** different countries: 1. a country before landing in China 2. one and only ONE city in China (among those offering those free visa). 3. leaving for another country (including Hong Kong, Macao).

Separate tickets are fine. It doesn’t need to be one ticket.

Thanks for the information. When I ended up with a transit in China before Beijing then I got confused about it. I concluded that somewhat the airliner that brought us in China HAD TO prove that it would take us outside as well .... which means ... on the same ticket (==>itinerary).