Inosuke doesn't become a Hashira in the manga. The story progresses with him having other significant experiences and achievements instead of achieving that specific position.
It's hard to give an exact number. Different story arcs and battles led to the deaths of multiple hashira. Some died heroically, while others met their fate in unexpected ways. The count changes as the manga progresses.
Definitely not. Genya remains outside the ranks of Hashira throughout the manga. This is because of a combination of factors such as his skills, experiences, and the overall direction of the story.
Demon Slayer left off in the manga Hashira at a cliffhanger moment. The heroes were at a crossroads, and the fate of the world hung in the balance. It was a point that left readers eager for more.
I think Warhammer 40k fanfics are a great way for fans to explore the vast and complex universe further. A good fanfic can add depth to the existing lore. For example, it might focus on the daily lives of the Imperial Guardsmen, which we don't often get to see in the official works. But there are also those that are just not up to par. Maybe they lack proper grammar or have a really convoluted plot that doesn't make sense in the context of the 40k universe.