For reaction 1, the products are: Cl-, NH4+, NH3, H+ (as HCl is strong acid while ammonia is weak base)
For reaction 2, the products are: Na+, H2O, NO2- (NaOH is strong while nitrous acid is weak. No HNO2 because the H+ will react to form water so equilibrium will shift to the right in equilibrium HNO2 → H+ + NO2-)
For reaction 3, the products are: NH3, NH4+, HNO2, NO2- (both are weak)
Reaction 3 is probably creates a buffer solution as they can accept or donate protons and the equilibrium will shift.
If acid was added to reaction 2, the NO2- will turn to nitrous acid but if base was added, nothing will happen, so not a buffer solution.
If acid was added to reaction 1, the equilibrium NH3 + H+ ↔ NH4+ will shift to the right and if base was added, the equilibrium will shift to the left so it is a buffer solution.