It could be a polygon with 4, 6, 8, etc vertices.
A four-sided polygon with congruent sides and angles, and two pairs of parallel sides.
An irregular polygon is a plane (2-dimensional) shape which is bounded by straight lines that meet in pairs. If all the sides are congruent AND all the angles are congruent then the polygon is regular: otherwise it is irregular.
two pairs of congruent angles in a rhombus
Yes, both pairs of opposite angles in a parallelogram are congruent.
No, not all angles in a trapezoid are congruent. A trapezoid may have two pairs of congruent angles, or may have no congruent angles.
A rectangle has 4 congruent angles. 90 degrees. It is also a parallelogram, 2 pairs of congruent sides.
Such angles are called vertically opposite angles.