Upstairs is nice and most people are dressed up. But it isn't required.
Nothing required, but eating in the dining area upstairs would be a place for business casual or dressier. The bar area on street level is fine for a more casual appearance.
Jean's and nice top is acceptable
From team jerseys to special date dress
No, casual is fine, but it's a nice restaurant so you might want to look respectable.
Not that I've noticed
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