Q1. Now will this Gift to my Grandmother is legally valid? Where so called gifted property is mentioned in Registered Deed 1987.
If the gifted properties has a mention in the registered partition deed that were registered in the year 1987 and have been accepted by other shareholders, then it can be considered to be valid.
Q2. Are the Deed registered in year 1987 legally final for property settlement among all three Grandfathers?
If it was mutually agreed by all the shareholders and there was no dispute on that among them then it can be considered as final settlement among them.
Q3. Can Grandsons get his share in proper if property is not equally settled among my fathers & Uncles? (After all its Grandfathers Property against Registered deed 1987)
The grandsons do not have shares in the grandfather's properties.
Their fathers may have a right to a share in their father's properties provided they have died intestate.
Q4. Will the proper firstly partitioned among "Father & Uncles" and then Grandsons will get the share from their respective fathers share?
Even if your grandfather's share in the properties are partitioned among his children, the grandchildren do not have any rights in such partitioned properties even through their respective fathers.
Q5. My Uncles (Four out of Six) has filed a complained in Sub Division Magistrate (SDM) Court to help in partitioned the property among 6 Brothers. Now what should be Our Stand (Grandsons) against this Complain?
As said, during the life time of yor father you as a grandson do not have any rights in the property, your father can participate in the legal proceedings of the partition suit.
Q6. Is there any possibilities of Property Re-Partitioned at fresh note among 3 Grandfathers if refuse to accept Registered Deed 1987?
There are no possibility r reopen the same if the parties to the registered partition deed of 1987 are not living anymore.