1. reaction rate always increase with temperature. in fact, the equilibrium constant is the ratio of the forward rate constant to the backward rate constant. increase in temperature increases both the rate constant, so reaction rate increase as well. however, the position of equilibrium will adjust to the reactant side.
2. ammonia is a very weak alkali, so it won't be able to act as an effective buffer. conversely, HNO2 is a much weaker acid to HCl, and thus it can act as a base in the presence of HCl.