Hey Janak,
According to the parts manual; looks like the metal support piece is attached to a part of the rear axle, piece #24 holding to piece #13:
I'm not sure if you have to take the rear wheel off, I don't have my bike with me to check out. You should be able to remove the sprocket side nut locking ring and axle nut, 5 sprocket nuts and be able to pull the sprocket off?
Don't hold me to it