Implementation timeline extended for manufacturers under GST; commencement remains backdated to the original effective date. Amendment replaces the original operative commencement date in paragraph 4 of Notification No. 198-F.T., extending the implementation deadline for manufacturers of specified goods to a later date. The amendment is declared deemed to have come into force from the original prescribed commencement date, thereby maintaining retrospective effect of the notification while substituting the implementation timeline for compliance under the West Bengal Goods and Services Tax framework.