Can I make registration of apartment after 16 years

Dear Sir I purchased a flat/apartment in southern part of Kolkata in the year 2000. There was a sale agreement made based on the that I made the payment to the developer. I got possession letter as well as mutation certificate from Kolkata Municipal Corporation. However, the property was not registered partly because of developers' lethergy and rest because of my fault. Now, I want to sell the apartment to a third party purchaser. When I approched developer for fresh registration request, his concern was, if now the property is registered from his firm's name to my name, he has to pay huge taxes because of increase in valuation of property for last 16 years so he is dillidallying the matter without showing much interest. Now my questions are: 1. Is it true that the developer has to pay good amount of taxes for registration bacause of escalation of property valuation? 2. Is it possible to directly have the registration between developer and new purchaser? 3. From new purchaser point of view, whether he is eligible to get the house bulidng loan based on in the present status ( he has no financial problem only concern is the papers are okay). 4. Any other prospective solution which would have lesser financial impact on developer and myself. Appreciate early response from concerned. Thank you very much in advance. Saikat Ghosh