1).Can the Developer's Agreement be cancelled after elapse of so many years(1995 to 2015), a civil suit is already in progress for almost 10 years and what will be it's purpose when the developer has already done what he intended to do ie. sell part of the property, get money and has now fled the scene without legalizing his works properly? Do we really get some benefit by cancelling the agreement now ?
The developer's agreement if in force as on this date, it may be cancelled due to breach of conditions of contract. Since you have already file a recovery suit, let the case be progressed in its own stride, in the meantime you may avoid further damage by the developer on the basis of the inforce agreement, though he has actually fled the scene by swindling the money, what is the guarantee that he may not operate from remote location with the same type of fraudulent activities.
2).Can we challenge the validity/legality of the POA made in 1995 on a Rs.50/= stamp paper and only notarized, now in court and then the subsequent documents made by the developer based on the POA.
The POA deed if not cancelled at the time of his alleged illegal transactions that time, the same has to be challenged on the basis of legal validity only.
3). Can the defendant's bring in new set of documents as evidence or exhibits at this 1st appeal stage to prove their case or remove some existing documents to suit their purpose.
Let them file any new document, you have rights to object them for creating records to fill up the lacunae. First wait if they are bringing any such new evidence, verify the veracity and then challenge their legal validity.
4). I get to know that an unregistered and not duly & properly stamped MoU ie. on a Rs. 10/= stamp paper cannot be taken as evidence in the court and also cannot be taken as a deed of assignment as granted by the Judge. Please confirm, can you site any case laws for it.
There are various settled laws to confirm that the unregistered documents in this regard are not admissible as evidence. You may contact your lawyer who will be able to get them.
5). Can we file any criminal case against the developer or the occupants now after a gap of so many years ie. from 1995 to 2015-will that be sustainable and beneficial ?
You should have done this long ago, at this stage he take a defence that since the matter is before a civil court, this is not maintainable. However f you have influence with the higher police officials, you may try to put pressure on the local police through them by lodging a criminal complaint.