What is the name of the quadrilateral which has diagonals that are different in length and has two axes of symmetry?

The quadrilateral you are referring to is called a kite. A kite is a quadrilateral with two distinct pairs of adjacent sides that are equal in length, and one pair of diagonals that are not equal in length. Additionally, a kite has two axes of symmetry, which are lines that divide the kite into two congruent halves.