  This is a continuation of our series of works for the inhomogeneous Boltzmann
equation. We study qualitative properties of classical solutions, precisely,
the full regularization in all variables, uniqueness, non-negativity and
convergence rate to the equilibrium. Together with the results of Parts I and
II about the well posedness of the Cauchy problem around Maxwellian, we
conclude this series with a satisfactory mathematical theory for Boltzmann
equation without angular cutoff.
