I'm not entirely sure specifically what 'black rule obeah scool stories' are. 'Obeah' is a form of folk magic in some Caribbean cultures. It could be stories related to some sort of rules within a context that involves black magic or obeah in a school setting, but without more context it's hard to say for sure.
There's no way to tell without more information. They could be completely fictional, made up to entertain or to teach a moral lesson. Or they could be based on real events that have been exaggerated over time. Maybe in some Caribbean schools where obeah has a presence in the local culture, there could be some real - life incidents that inspired these stories, but it's just as likely that they are pure fantasy.
Yes, there is a manga for Visual Prison. It typically follows the core elements of the Visual Prison franchise while potentially adding new layers and nuances to the story and character development.
The ending of the School Prison manga is quite unexpected. The main characters manage to overcome their challenges, but there are some loose ends that leave you thinking.