Resale Flat Corpus Fund

Dear legal experts, I have few queries regarding bylaws of residential communities. I bought a resale flat in Visakhapatnam in End May 2020. It was resale property. During this transaction there was already resident association formed. seller told me they alteady paid corpus amount.But now the association is asking me to pay a corpus of Rs. 20k as I'm resale owner. My queries : (i) Is association has any rights to demand corpus fund from me which previous owner already paid, Is this legally valid? (ii) my seller has 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 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?