1. Since the Release Deed is adequately stamped and registered in the Sub Registrar's Office in the year 1998 in favour of your grandfather, then your grandfather was the owner of the property and the Gift Deed executed by your granny in favour of your uncle is not legally tenable and same is Null and Void.
2. Get the Encumbrance Certificate to know whether the release date executed by your granny in favour of your grandfather reflects the transaction.
3. Also check whether the mutation of the property in your grandfather's name had been effected subsequent to the Release Deed.
4. File a case in the competent court to cancel and declare the gift deed executed by your granny in 2005 as Null and Void, since your granny was no longer the owner of the property in 2005, in view of her executing the release deed for the same property way back in 1998 itself.