So is the energy produced by flashlight batteries. Just because the quantity is small doesn't mean it is any less obedient. Yes, mass change from outgassing, or even from dust accumulation would be far greater. That doen't mean there isn't also a mass change from energy conversion.
I don't know where you got that information from. Can you lead me to a reputable link on the same? I'd be grateful.
No.
Mass is not consumed in the electrochemical reaction that takes place in a battery.
The E=mc^2 equation applies to a closed system.