See also: When should I close a question as "Too Story Based"?
Asking about plot elements such as the actions of characters, rather than about the world in which your story takes place, is off-topic on Worldbuilding. Capabilities of characters within a world and creation of groups of characters (like nations) are on-topic, but questions must focus on what is possible or likely to develop, not what someone would or should do.
Questions about the back story of a character are also prone to being Too Story Based. Checking whether a specific element of a back story that you have already written is possible or likely is probably on topic; however "write this for me" is not. You should also be careful to explain why the back story is relevant to the world and building that world, rather than being just development of that character.
This is because only the person who is developing a plotline can decide how characters will act or the plots will develop. Worldbuilding can determine what is possible, but the choices about what happens given those possibilities belong to the author.
