Symmetry Lines

Draw a polygon and determine the number of symmetry lines it has. If you modify your drawing by changing some of the side lengths, will it contain the same amount of symmetry lines?

In what case(s) will the polygon have the most possible symmetry lines? Do you get the same results with any other polygon you choose? Can you make a prediction for the most number of symmetry lines in a n-sided polygon, or a n-gon?