Just make sure your story pertains to the category's general theme. For example, I doubt many would appreciate seeing a space adventure posted within Fantasy's story-board. It is true that many stories span many genres of literature, but every story leans more towards one theme then another. There is a reason why the story's creator posted it in a particular category. Yes, but only in moderation and good taste.
Foul language is a tool for authors, but only when used wisely.
Basically, use common sense and you should be able to avoid my negative attention. Yes, mature content is allowed, but we respectfully ask that you note such a story as mature in its description. No, this ability would be too easily abused so it has been removed. If your story is of high quality, however, and near completion already it is possible to seek having it permanently published on a page of its on within FWG's domain. Anyone can review a story, but we encourage all users to be respectful to the author in your opinions.