1. It is unclear what is the nature of the document which you claim was executed by your grandmother in your favour in 1998, but it seems to be a family settlement or gift deed, both of which required mandatory registration under the law.
2. During your grandmother's lifetime she was at liberty to revoke the instrument of transfer, if any, executed by her, but this is subject to the condition that the transfer was to take place on a future date. If the transfer of property had, in pursuance of the instrument of transfer executed by your grandmother, taken place, she could not have cancelled it unilaterally.
3. Without a threadbare perusal of the document it is not possible to formulate any opinion. You should get the document vetted by a lawyer to know where you stand.