2.
Similarities:     a. Both figures are made of line segment.
                        b. Both are closed figures,
                        c. Both are plane figures.
Diffrences:
                        a. In square all angles are right angles but in triangle only one angle is right angle.     
                        b. Different number of line segments in both figures.
                        c. Different sum of all the angles in both the figures.
3. 
Similarities:
                        a. Both figures are made of four line segment.
                        b. Both are closed figures,
                        c. Both are plane figures.
Diffrences:
                        a. One figure is kite while other one is rectagnle.
                        b. In one figure all angles are right angle but not in another one.
                        c. In one figure both diagonals bisect each other while in other only one diagonal.

4.
Similiarities:
                        a. Both are closed figures,
                        b. Both are plane figures.
                        c. One pair of opposite sides in both figures is parallel.
Difference:
                        a. In one figure all segments are line segments while in other one segment is curved line.
                        b. Area of one can be calculated easily by a formula but for other there is no direct formula.