I don't have definite information. It could be loosely based on some real incidents, but it's likely to have been heavily fictionalized to make it more engaging for the audience.
Not entirely. While the movie might have drawn inspiration from real events, it has undergone significant fictionalization and creative interpretation to make it more engaging for the audience.
Well, 'Unbreakable' is a work of fiction that draws on the idea of the superhero archetype in a more grounded way. There isn't a specific true story that it's directly based on. However, it could be seen as taking inspiration from the general human fascination with extraordinary abilities and the idea that there could be people with such powers hidden among us. Shyamalan used this concept to create a world where a man discovers he has superhuman strength and invulnerability, while another has a different sort of power related to his frailty.