No.
The centre of mass of a rectangular lamina lies at the point of intersection of its diagonals.
A rhombus
A quadrilateral with four congruent sides and uncongruent diagonals is a Rhombus. See related link for a picture
diagonals.
Rhombus.
Square.
It is a square.
square
rhombus
They are called diagonals.
A square.
A square