No, it's not. Devotion is typically a fictional creation that may draw inspiration from various elements but is not directly based on a specific real event or person.
Hard to say. It could be a blend of real and made-up elements. Maybe the author took some real-life experiences and built a fictional narrative around them.
It's hard to say for certain. Sometimes movies draw inspiration from various sources, and Devotion could be a blend of real and fictional elements to create a compelling narrative.
"A Hero Reincarnated as a Demon King" was a light novel written by the author, Immortal Blade. One of the tentative worlds was the endless Fafnir of the Gun Emperor. The plot of the novel was about a brave man who was cursed to become the new demon king while fighting against the demon king. He was abandoned by the world and his adventure had just begun. If you like this topic, this book is a good choice. I hope you like this fairy's recommendation. Muah ~😗