Registration of flat

I purchased a flat in 2007 in Durgapur, West Bengal but it never got registered till date. The builders had some internal issues with the government due to which the flats never got registered. Also, the payment reciepts that were issued in 2007 mention a transfer of ownership clause for the flat. A public bank paid the entire amount in advance for the flat against a loan on my name. However, few years ago they got us sign on the registration papers that mentioned a 999 year lease but it again was not executed due to some internal issues on their end again. Now, they further want to change that term to a 99 year lease ( directly at the time of execution of registration ) without intending to refund any money for the remaining 900 years. Some of the purchasers in the same apartment society have got a 999 year lease executed, though. I want a transfer of ownership or a 999 year lease with a full right of resale. Please advice as a 99 year lease seems to be a trap with the value of the property diminishing every year.