Can an individual learn English language by practicing only the English literature (novels, non-fiction, poetry, and plays, among other forms)?

Answer 1

My short answer is yes. Is it harder, I would also argue that depending on who you are and how you learn. I have a buddy in Japan that is completely fluent in English, and has never taken an English class one day in his life. He learned from movies, and TV shows while growing up. The same could be said for people learning Japanese off of Anime. It is fully possibly you just have to be careful in picking up bad habits from shows, like incorrect grammar, or slang that might be really offensive to someone if you don't know the meaning of it.