Whether your answer would be same if in 2017, B and C had taken a new partner D and then filed a suit against X without fresh registration ?

Further in 2017, B and C had taken a new partner, D, and then filed a suit against X without fresh registration. Where a new partner is introduced, the fact is to be notified to Registrar who shall make a record of the notice in the entry relating to the firm in the Register of firms. In this case, the second condition that partners suing should be named as partners of the firm is not fulfilled, as the name of D is not registered. Therefore, the suit filed after D joins the firm without registration, is not maintainable.