Corpus fund in case of resale property buying

Dear legal experts, I have few queries regarding bylaws of residential communities. I bought a villa in Bangalore in 2016 Feb. It was resale property and the seller had obtained no dues certificate from builder before selling to me. During this transaction there was no resident association formed. Later in end of May 2016 association got registered. Now the association is asking me to pay a corpus of Rs. 25k as I'm resale owner. My queries : (i) Is association has any rights to demand corpus fund even for transaction which happened before its formation and registration? Is this legally valid? (ii) my seller bought NOC from builder before selling. It means all dues are paid including the corpus. So is it right that whatever number of times property gets transacted, every time to charge corpus from buyers? (iii) If in case any amendment to bylaws will be done now to include transactions to pay corpus fund happened before association formation/registration date, will it be valid in legal terms? (iv) is the corpus fund non transferable strictly generally?If an association has all rights to carve its own regarding this to explicitly make corpus fund as non transferable from buyer to seller in case of transaction?