Yes, they can be. They are available as "X-8 Breath Guard" and "Chin Curtain A."

No0, they aren’t. they are fixed permanently.

Please wipe with cloth dipped in solution of neutral detergent. SHOEI doesn’t recommend to wash a helmet dipping in water because label for standard may be peeled off or printed letters may disappear.

Please refer to "How to Maintain Helmet" for detail.