I'm hoping someone can advise. I am traveling to Japan at the end of April and have two 6/7 hour layovers in Dubai (1 outbound and 1 inbound)

From reading other forums I've heard people say that the Dubai airport will be sufficient to keep me occupied, however I've like to leave the airport and stretch my legs on the outbound flight (especially as I've never been to Dubai before)

My flight land at 8pm and my next flight departs at 2.45am local time (a total of 6h 45m).

1. Is there anything to do in Dubai at this time? (late evening)
2. Is this sufficient time to leave the airport, go somewhere to eat (maybe a little sightseeing), get back to the airport and check-in?
3. Do I need a visa to enter Dubai for 6 hours?
4. Any recommendations on where to go, what to eat and what to see?

Any help or experience is appreciated!