I'd suggest looking on dedicated manga apps such as Manga Plus or Crunchyroll Manga. They often have a wide range of titles available, including Chained Soldier.
It's hard to pinpoint exactly. The ending point can vary depending on how the anime adaptation was structured compared to the manga's original storyline.
Well, without having read it specifically, I can only guess. It could be about a military - themed story where the soldiers are connected in some way, like in a chain of command or a more metaphorical sense. There might be a plot that revolves around loyalty, sacrifice, and the struggle for power within the military structure. It could also introduce some supernatural or fantasy elements that are common in light novels to make the story more exciting and engaging.
A chained novel is a type of collaborative writing. It's where multiple authors contribute to a single story, one after another. Each author adds a chapter or section, building on what the previous author has written. It can lead to really interesting and diverse stories as each writer brings their own style and ideas to the table.