Question

an expert who demands high standard in arts and literature etc... Please give one word answer for this

Answer 1

An expert who demands high standard in arts and literature - There is no one word for it.  They are known as "Literary critics".  Normally a group of people will be appointed for judging the work of art and literature.  If you need one word, you can use "Perfectionist" because those are the people who never get satisfied with "one go".

Answer 2

Answer - Connoisseur

It refers to a person who is an expert judge in matters of taste. He is an expert judge of, an authority on, or a specialist in some field. For example a connoisseur of music. He has a lot of knowledge about some art. He is competent to pass critical judgements about any art specially fine art. He understands the details, principles and techniques of an art.