Visa-free with no seat number for departing flight

Hello, I am flying from Prague (CZ) to Beijing, there I have stopover for 42 hours, than flying to Sydney (AU). I have two separate electronic tickets (flying in and out of Beijing). My seat will be allocated at the baggage drop at the day of departure. The airline probably doesn't have online check in. Is this going to be a problem for 144-hour free transit? Thank you.