no they dont
In general, a square. A square always has 4 lines of symmetry. A pentagon need not have any. Only a regular pentagon can have 5 lines of symmetry. But if you created pentagons from sides with random lengths then, assuming the pentagons existed, only a tiny fraction would be regular: most pentagons would have no axes of symmetry.
triangles
A square has four; a pentagon has five.
This depends on the type of prism. If the shapes on the ends are pentagons, the prism has 6 planes of symmetry. If they are hexagons, it has 13 planes of symmetry. It has the same number of planes of symmetry as the shapes on the end have lines of symmetry, plus 1.
Not if they are regular 5 sided pentagons
If you're talking about convex polygons with equal sides (eg. equilateral triangles, squares, pentagons, hexagons, etc.), then the relationship is a very direct one. In those cases, there are as many lines of symmetry as there are points in the polygons. A triangle has three lines of symmetry, a square has four, a pentagon five, etc.
regular pentagons have no parrallel lines. irregular pentagons might but it depends. :))
The square is the only one I can think of. The lines are vertical, horizontal, and both diagonals.
2 lines of symmetry
it has five lines of symmetry
A nephroid has 2 lines of symmetry.