Note the use of the phrase "closed surface" in Gauss' Law, which means that the surface has to enclose a volume, although there are no limits on the shape. That said, Gauss' Law is best used when the surface has sufficient symmetry (e.g. cubes, spheres, cylinders, etc).
3.1 Revisit 1.1 with knowledge of Gauss' Law.
3.2 Given any number of charges of any magnitude and sign, is it possible to arrange them such that there exist a point where a test charge may be placed such that it will be in a stable equilibrium no matter which direction it is displaced in?
3.3 If a electric field is 0 throughout some region of space is zero, does it imply that there is no charge in that region?
4. Dipoles
Consider two charges of equal magnitude q but opposite signs at a distance d apart. We define the dipole moment of this set-up as: