I am arriving on HK Cathay CX90 at midday Sat but don't fly out until 3:30am Sun on Siberian S7.

.. I am assuming I will need to pick up baggage and clear immigration with 72hr visa as they are different airlines/tickets. So I wont be able to check into s7 flight until much later when they open check in in area C. Is there a hourly lounge/place to sleep before departing customs security check? ie. from departure hall?

Most appreciated.