Vat act on interstate sales

KINDLY PLEASE REPLY AS PER VAT ACT 2006,WHEN INTERSTATE SALES MADE PRIOR TO 11.11.13 AND AFTER 11.11.13,IS ITC REVERSAL TO BE CONSIDERED:-   (a) IF SALES WITH C FORM ?

(b) IF C FORMS NOT PRODUCED AND DIFFERENCE OF TAX IS PAID?

(c) IF SALES WITHOUT C FORM? KINDLY PLEASE REPLY...    

KINDLY PLEASE REPLY