For Hanoi, you really need three hours for your departure. You can get ahead of the ID check line to reach airside if you hold a Business or First class ticket. However, once airside, there is no fast lane.

At passport check counters, foreigners and locals use the same lines. It took me more than one full hour just to go through this and I was flying business class.

I think you can hire a driver to give you a quick tour. 10 hours isn't that much time however. Happy travels.