Well, it's hard to say for sure. The concept of 'porn-like' is quite subjective. Some might consider certain novels with excessive sexual descriptions as such, but it depends on individual perspectives and cultural standards.
The first appearance of lesbian porn stories online is difficult to determine precisely. It likely occurred gradually as the internet grew and different types of content became available, without a clear-cut beginning.
Alexa cannot play porn novels. It's a platform that focuses on providing legitimate and family-friendly content. Any such inappropriate material is strictly prohibited.
The main distinction of porn with a story genre from regular porn is the presence of a coherent narrative. Regular porn often jumps straight to the sexual action, while the story genre tries to add some kind of story framework around it. But in the end, both are adult-oriented and feature explicit sexual content.