Bl&lro mutation issue

I have identified a property comes under Sonarpur Police Station, Kolkata - Piece of land and a already built 2 storey independent house. But land Classification as in BL&LRO mutation was done as 'Bagaan'(Garden) with current owners name. But Bank refused to provide home loan as it not recorded as 'Baastu'. Couple of another properties are there which registered as 'Doba'(small pond) or 'Danga'(highland) too. But they have proper plan sanctioned for the building more than 20 years ago. Can you please advice on below 2 scenarios : 1) Is this possible to convert those lands to 'Bastu' by the current land owner? Asking because the house is already built. This should have been done before the construction started many years back, my understanding though. 2) If I buy the property with the current classification, (of course if I get loan from any financial institution) - can I convert the land as Bastu later on in my name? what's the legal process, difficulties etc in such scenarios? I appreciate your help here.