Yes
sometimes
Sometimes they are.
sometimes
Never
Yes
sometimes
Sometimes they are.
Parallelograms are squares is sometimes true. Squares are parallelograms is always true. Rhomboids are parallelograms is also always true. So not all parallelograms are squares but some are.
sometimes
Sometimes similar but it depends
sometimes
Never
Sometimes.
If they are congruent they must be similar.
Perfect squares will never be irrational numbers. A perfect square is the result of multiplying an integer by itself, which always yields a rational number. Since the square root of a perfect square is an integer, perfect squares are always rational. Thus, they cannot be irrational.
Some parallelograms are squares - the ones which are equiangular (have equal angles) and are equilateral (have equal side lengths). All squares are parallelograms, but only some parallelograms are squares.