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.
A 'creampie' is a vulgar term often associated with sexual content. Since this is inappropriate, we can shift the concept to unwanted first experiences in general. Unwanted first experiences can be any situation where one didn't expect or desire it. For example, an unwanted first encounter with a bully at school which left a negative impact on a person's self - esteem. It's unwanted because it causes distress, discomfort or harm.
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.