Retirment and admission in partnership firm

One Partnership firm having two partner Mr.A and Mr.B. After two year Mr. B left the firm as a retirement partner and the firm become dissolve, and the said Retirement cum dissolve deed was file with Sales Tax Department but not inform to ITO. But the business was continued under same VAT No and PAN NO. and after one month one new partner is coming in to the business as a new admission and a new Partnership deed is prepared. Now my question is-

1. Whether the same TIN (VAT) No can be continued after the change of partnership.
2. Whether the same PAN No. can be continued.
3. Or surrender of existing PAN No. and applied for a new PAN No.
4. If there is two pan card then we have to file two separate Income Tax Return for a single financial year i.e. after retirement and admission.
5. We have to applied for amendment with Sale Tax Dept with New Partnership Deed and the same TIN No continued.

Please help  me