A quadrilateral or tetragon.
Polygons
Both rectangles and squares are polygons. A square is a special case of a rectangle.
Squares are polygons, but not all polygons are squares.
A set of polygons might have such shapes in it. Certainly the set of all polygons does. So does the set of all polygons with fewer than 5 sides. Many other examples could be given. I am avoiding the use of the word "group", because it has a technical meaning in modern algebra.
the answer is a square
they are all polygons
Regular Polygons. eg - Square is a regular figure, but a trapezium is not.
A square is a special type of polygon.
They are polygons.
they are both polygons
They are both polygons.
There are no such things as thirty polygons, but I can try to help you name thrity: square square square square square square square square square square square square square square square square square square square square square square square square square square square square square square. You are welcome.