At least 3 sides or more
it seems to me that the only polygon of your description is a square
A type of polygon is a rhombusial polygon, trysectalnict polygon, and a equilateral polygon.
A triangle (not traingle) is a polygon. It can be a regular polygon but need not be.
an arrow is or isn't a polygon?
No, a convex polygon cannot have an interior angle sum of 400 degrees. The sum of the interior angles of a convex polygon is always equal to (n-2) * 180 degrees, where n is the number of sides. Since the sum of the interior angles must be greater than 180 degrees for each interior angle, a convex polygon with an interior angle sum of 400 degrees would require at least 9 sides, which would make it a nonagon, not a polygon.
Polygon B is an octagon.
The definition of a irregular polygon is any polygon that is not a regular polygon.
An equilateral polygon is a polygon where the length of all the sides of the polygon are the same length.
Regular polygon Equilateral polygon Polygon with rotational symmetry
No, but a hexagon is a polygon.
By definition, a regular polygon has all interior angles the same, but a concave polygon has some interior angles that are not identical. Also, it violates the axiom that all vertices lie on a circle.While it is possible to construct a polygon with equilateral sides, to be concave would require a form that is equally convex and laterally opposite. (An example is a 'solid arrow shape.')
If it had n sides, the sum of its interior angles would have been (n-2)*180 degrees. That would require (n-2)*180 = 1140 This requires that 180 divides into 1140. It does not so there is no such polygon.