Is it possible to refinish floors one room at a time?
You could install a thin threshold between each room. That would cover the overlap in finish between the rooms.

If the planks run parallel to the doors, you could cut out one board between the two rooms. That would give a clean line between finishes (and place the one board back at the end.

All that said, you will save a TON in labor if you just do it all at once.