With that long a connection, assuming you don't want to exit and go to Dubai and possibly get a decent hotel room for not much money, then the best kept secret is going to the Concourse A J lounge, and go to the very far end of the lounge and go down a level to the "quiet zone" which is usually deserted and has loungers and blankets provided that you can sleep on. However, I would advise you to bring earplugs (which you can get on board) and eyeshades, in case eye shades are not laid out when you visit.

However, the lounge is relatively insecure when it comes to baggage storage, and the area is not lockable etc. Your paranoia may vary

You won't need to reclaim baggage. However with that kind of connection, I'd arrange a hotel in DXB instead - they are inexpensive (if you don't get Dubai Connect).