Sukuna does die in the manga. The way it happens is quite dramatic and ties in with many other elements of the story, adding depth and tension to the overall narrative.
Nope. Ryomen Sukuna has no basis in reality. It's a product of the creative minds of the writers and illustrators who designed a captivating fictional character for the enjoyment of the audience.
Well, that's hard to say. Maybe it was a main character trying to involve someone new in the story. Or perhaps it was a side character with a specific purpose. It really depends on the context and development of the manhwa.
You can search for the manga you want on Baka Updates and click on the available links. Sometimes, you might need to create an account or follow specific instructions provided on the site.
In the manga, Sukuna doesn't possess all 20 fingers. There are specific story arcs and events where his finger count changes based on the plot developments.