Whether there exists a possibility that matter can be converted to something (or some state )other than energy?
Everything (whether massless or not) has energy.
So even that state (whatever it maybe) has to have energy.
to my understanding , it is not possible..
it will not only violate law of energy conservation, but, also momentum conservation.
For that we need that 'some other thing 'to whoch w can convert that matter.At present all Forces,and everything can be expressed as funct of Energy.
If someone considers that gravity is not a form of Energy(as we define it) and terms a separate idea for it,then i think matter can be linked to gravity,so it all depends on what you call Energy!
Consciousness exists.We still don't the connection of consciousness with energy and matter.Of course consciousness will not exist without energy and matter.