GST rule amendments change timelines, ITC declaration timing, gold import credit reversal, payment routes, and registration forms. The amendments extend a sixty-day period to ninety days; allow Ministry of External Affairs recommendations in processing the specified form; require electronic declaration in FORM GST ITC-01 within thirty days to claim input tax credit; restrict carried-forward credit for additional customs duty on imported gold dore bar to one-sixth with five-sixth debited on supply; prescribe fifteen-day validity for FORM GST PMT-06 challans and alternative payment routes for certain non-resident online suppliers; require Joint Commissioner-level membership on the Authority for Advance Ruling; and revise registration and TRAN-1 form provisions.