How can a member protect rights in redevelopment agreement dispute?

Sir, Our Redevelopment Agreement had a provision for a ₹15.80 lakh bank guarantee. At the request of the developer, a supplementary redevelopment agreement was executed and registered, under which the developer agreed to mortgage his saleable component of the first floor. He also agreed to execute a mortgage deed and pay the applicable stamp duty. However, I have discovered that the premises he agreed to mortgage have already been sold. We came to know about this when renovation work started in that premises. The office bearers never informed the members, and no consent was taken from us. Most members have no objection because they are not aware of this matter. The secretary is threatening members that if we raise objections, he will stop paying the rent. My PAA (Permanent Alternate Accommodation Agreement) has also not been executed yet. Kindly guide me on how an individual member can protect his interests. I am a senior citizen aged 71 years and I fear that I may not receive my flat in my lifetime. Kindly guide me.