As many as you want - up to six. "Hexagon" simply means that there are six sides.
You decide how "alike" they are. A square has four sides; a hexagon has six. In a square, all sides have the same length, all angles have the same measure. In a hexagon, this may or may not be the case.
Yes, a regular hexagon has ALL sides the same length and ALL angles equal. If you flatten it somewhat (like the profile of a lens) then the sides may still have the same length but some angles will be larger than others if opposite angles are the same than there will be symmetry. (there are many other options to retain symmetry in a hexagon this is but one)
The difference between an irregular and regular is that a regular shape is the normal form of a hexagon or pentagon etc. A regular hexagon would have six sides all the same length and all the angles would be the same. An irregular shape is a shape in a different form of the normal form. Example, A irregular hexagon would still have six sides but the lengths may be different and the angles also may be different.
A 6 sided hexagon has 6 sides but no edges
There need not be any.
Every hexagon has six sides. That's what the "hex" in hexagon means. Every polygon comes in two flavors and the hexagon can be either one of them ... 'regular' or 'irregular'. If the hexagon is a regular one, then all six of its sides are congruent. If the hexagon is an irregular one, then 2, 3, 4, 5, or none of its sides may be congruent.
Adjacent sides of a parallelogram may be of different length. In a rhombus all four sides must be of the same length.
You measure them. In some cases, you may know some other information about the hexagon, in that case you may be able to calculate them.
A regular polygon must have all sides (and angle) equal.An irregular polygon does not have to have all sides equal, but some may be equal.An irregular hexagon may have 2, 3, 4 or 5 equal sides.
6 of each.
Two sides have the same length as each other. The other side may be shorter or longer in length than the other two sides.
A three sided polygon in which two sides are equal in length and two angles are equal in size. Two sides have the same length as each other. The other side may be shorter or longer in length than the other two sides.