1. contract is with the society. so society can file a suit against the builder. the suit can be initiated on behalf of the society by its authorised signatory
2. court fee will have to be paid depending on the claim amount. If the claim amount is above 1 crore then suit can be filed in High Court. If below 1 crore then in city civil court.
other charges will usually be the lawyer fees, clerkage
3. unpaid rent with interest can be claimed in the suit
4. you can terminate the contract with the builder. Or if you want to continue with the same builder then seek directions from court to this builder to comply with the obligations under the redevelopment agreement
5. apply to the BMC or if the builder has registered the project with RERA then all these permissions will be uploaded on the RERA website. You can also write to the builder to provide certified copies of all the permission obtained by him
6. yes a power of attorney can be given.
if the society MC is not in favour of the suit then the aggrieved members duly represented by their power of attorney holders can file the suit against the builder and society and other opposing members