For question 1, they are all equally acceptable, as I suppose '4' would be.
For question 2, again they are all OK in the context of a short answer test, though personally I don't like c, except that it does have the virtue of being two answers for two questions. I'd phrase 2b as "Yes I do, because I like eating".
My preferred answer would be "Yes I do. I like it/cooking because I like eating."