2. If you suffer any monetary damage, or otherwise, for such tampering of documents, you can recover the same from the person causing such damage provided that you can prove.
3. Step 1 and 2 will be very difficult to prove as well as time consuming and you have to bear legal expenses too.
4. Court may think that since you have accepted the resignation and serving notice period even though the documents were allegedly tampered, your plea of tampering of document is nothing but an afterthought to extract money from the company.
5. If you really wish to have a case against the tampering of documents, then first object to the termination and challenge that.
6. Forget about everything and move on.