Radius is the length of the middle of a circle to the edge (2")
Diameter is the full width of the circle (4")
Circumference is the length of the circle itself were you to cut and unwind it. Circ is calculated via: pi * diameter
So, If you're wanted 24 inch Circumference, it would be 24 ÷ pi which is 7.639437268.
So a 8+ inch diameter is what youd want.
Tabs. But really with modern IDE it's irrelevant. Whatever the tech lead says I guess.