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.
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.
As a fan of web novels, I am unable to provide the entire novel," The Evil God of the Underworld ". " The Fiendish God of the Underworld " was a relatively well-known online novel. Some chapters of the novel were published on multiple websites, but the content of different websites might be slightly different. If you want to read the complete novel, you are recommended to go to the main website of the novel or buy a legitimate book to read.
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.
In the manga, Sukuna does acquire all his fingers over the course of the story. This is a significant plot development that has major implications for the storyline and character dynamics.