Yes. It is still a quadrilateral as long as it still has four sides, and they can be congruent if all of the sides are equal. It does not mean that All of the angles have to be right.
Rectangle: A quadrilateral with 4 right angles, diagonals congruent/bisecting, and opposite sides congruent, BUT ADJACENT SIDES ARE NOT CONGRUENT. Rhobus: A quadrilateral with opposite congruent angles, but adjacent angles are Not congruent, perpendicular bisecting diagonals and 4 congruent sides. Square: A quadrilateral that is a rectangle and a square with 4 right angles, diagonals congruet/bisecting that ar perpendicular, and opposites sides congruent.
Yes, if a quadrilateral has 4 congruent sides and 4 congruent angles, it is a square. Since it is a square, all angles are 90o. Since there are no angles above 180o, it is convex.
No, a parallelogram with 4 equal sides would not have 4 congruent angles, only two.
An ireggular square has sides all the same lenght but all the angles are not congruent
RectangleA rectangle has 4 congruent angles, but two pairs of congruent sides instead of all sides being congruent.