i dont have the seat number

Hi, I will be using the free transit in Beijing this week and again when I am back from Korea.

I am spanish citizen and my final destination is Pyongyang. My flights are from Sweden-through Beijing (where i will stay 2 days) and then to Pyongyang. On the way back the same process staying in Beijing for 2 days. I have my seat numbers for my flight Beijing-Pyongyang but they will give me the real visa for North Korea while I am in Beijing (so I would only have a copy before that). And for my flight back to Sweden on my return I do not have a seat on the plane yet even though the flight status is confirmed. Also, do I need to apply for the free transit? where?

Thank you so much for your help!!!!!!