If a plane doesn't connect to any pin or via, it's not a ground plane, just floating copper. Simply add a copper pour to the top layer, but don't assign a net to it.
Thanks for your reply,
I need the ground to be connected with stitching vias [ not with other fan out via's ]
ie. Ground plane should have flow of signals only through stitching vias, and it should get conneted to top pad components [ fanout or via ].
Then the answer is no. You'll have to manually add keepouts to the areas you don't want connections.
Thank u ........