This question does not make sense. First of all, "vertices" is the plural of "vertex", but you have used it in a singular context, which suggests that you don't know what the word means. Second, a vertex is a point, so it cannot have sides. The answer to the question might be "zero", but it's equally likely that several important words have been omitted from the question. If the question were written correctly, it could change both the question and the answer, entirely.
contact it to vertical side of the square
3
4
Do you mean vertical parallel sides? I think there is 4.
Two.
Depending upon its orientation (relative to vertical) none, 2 or 4.
where the sides are vertical.
A quadrilateral need not have any vertical sides.
A hexagon has 6 sides. The number of vertical sides can be any number from 0 to 3.
An octagon need not have any sides that are vertical.
It can have up to the number of sides on the base, but it need not have any.
Two bases and three vertical sides make 5 faces.