Is the 'Acceptance of Resignation' letter binding on the employer

I was wrongfully forced to resign and had pending leaves adjusted for some of the notice period and received the 'Acceptance Of Resignation' letter on the last day of the work. Now I am told by H.R that these leaves I availed is not acceptable now and they will cancel the 'Acceptance of Resignation' and will issue termination letter by backdating the last day as day before from which I availed the leaves that were pending and they have cited a clause on the offer letter for this. 1) Is the 'Acceptance of Resignation' letter issued on the company letterhead and signed by the H.R director binding as per law or can the company later withdraw the same unilaterally saying that was a mistake and inform the they will process termination? 2) What options do I have in either case if the answer to the above question is YES or NO. 3) As I already submitted this 'AOR' to my new employer, what to do if the company deny the same during verification. Dear Sirs please reply and help me. Thanks.