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.
To draw manga in all volumes, you need to have a good understanding of the characters and storylines throughout. Start with basic sketches and gradually build up the complexity.
To draw manga in all volumes, you need to start with a good understanding of basic drawing skills like anatomy, perspective, and composition. Also, study different manga styles to find your own.
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.
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.