What are various parameter limits for HVAC validation. If we have to treat a change in formulation do we have to take 3 compulsory commercial batch trials and then proceed for a permanent change in the 4th batch or we shall take 3 R&D trials and

What are various parameter limits for HVAC validation. If we have to treat a change in formulation do we have to take 3 compulsory commercial batch trials and then proceed for a permanent change in the 4th batch or we shall take 3 R&D trials and its study is enough?