Answer:
1) The connection between fluency and the proper sentence is the use of the convention in punctuation. So the conventions which are on the surface of writing are the specialist usage of the judgment in the structure of writing. And the sentence's rhythm is the fluency and flow of languages, sounds, patterns, like the way that its used on book plays.
2) The purpose of informative writing is to focus on the facts like what something looks like, what it is, and what it is made of. It can also increase the knowledge of a concept or a subject. In the other hand, explanatory writing focus on how something acts, works, and why are things actually happening.