Question

Why is gauss law applicable to non symmetric bodies?

Answer 1

Gauss's law is always true as long as we remain in the classical domain, but applying it directly is not always useful. We can easily use Gauss's law to find the electric field in cases where there is appropriate symmetry. The case of an electric dipole is not one of these cases. Any Gaussian surface enclosing an electric dipole encloses no net charge, so the flux through it should be zero; that is indeed true.