It starts at a specific point in the manga, but I can't recall exactly without looking it up. You might want to check some manga forums or dedicated fan sites for the precise chapter.
It's hard to say for sure. Both Sukuna and Gojo are incredibly powerful, and it could depend on various factors like their current state and the circumstances of the fight.
The scene of Sukuna's death in the manga is a climactic moment. It's filled with action and drama, as various powers and tactics are employed to bring him down. The build-up to this point is full of tension.
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.
No. Ryomen Sukuna is a fictional character from Japanese mythology and modern manga/anime. He doesn't have a basis in a true historical event or person.