Is consciousness unique for an individual?
Consciousness cannot be counted and not unique to individuals.
What happens when you go to dream ? You create the dream people and you perceive them. Does there is unique consciousness in the dream for each Individual ?
No, only you were Conscious and other individuals are objects for you. Similarly in this waking world you are Conscious and other are objects that you are seeing and believing to be real. Minus your perception there is no world. Like minus you there is no dream.
Secondly If we believe that Consciousness stay in the body like a soul, than it is also not possible because than it will become an object with attributes ( which can be counted , or present at particular location )
Scriptures have always said that Consciousness is without attributes, it is formless.
What defines an individual ?
Vedanta says that there is no individuals, Brahman is acting through this body and to whichever body it associates it think of himself as the same body. Like in dream I can associate myself with different bodies.
Individuals exists in ignorance or due to power of Maya. Like birds are attached to their newborn and they reproduce and raise family. Who told them to do so ? It is Maya ( Consciousness ) which is guiding every form.
Except memory there is no individual. One was not before the birth and will not be after death as a physical body, but as Consciousness one will be always present.