1. You have the full right on the said purchased property but have a liability to pay the amount standing in the name of the owner of the flat as outstanding. You should have taken NOC from the said Society beore taking part in the auction since it is a flat in the Housing society.
2. You can file a Writ Petition before the High Court against the Bank (if it is a PSU Bank) praying for an order upon the bank to refund you the amount paid by you to the bank and the registration charge with interest, damage and cost
3. It is a fact that unless you clear the dues of the Society, it may not permit you to make any entry in to the premises of the said society.
4. You have purchased the flat with all the liabilities and dues standing in its name including the electricity bill remaining unpaid by the earlier owner.
5. It is understandable that the bank will take that stand but you can argue before the High Court that the bank had nowhere specified about the said dues standing on the said flat and has acted dishonestly.
6. & 7. You can file the Writ Petition and seek refund of the entire amount as suggested above.
8. The Society will argue that you are not yet a member of the Society and your ownership is subject to your clearance of the dues and sending bill to you does not arise for the said reason.