What foods are best for people with ms?

Suggest you consider. Historically, the low fat swank diet seemed to improve the relapse rate, and two older nutritional studies confirmed a modest effect. A few doctors thought some foods to be harmful and looked at "pulse counting", but this has never been proven. Not a food, but vitamin d supplements seem quite important, as low levels result in worse outcomes.
Unknown. General balanced diet is best normally. I am not aware of special diet that has been proved for ms.