Currently using starter plan, coz that’s what I can only afford at the moment, so I decided to consider a task to become my projects, and subtasks as tasks. However these tasks will have their own subtasks which is now sub-sub-task, but these sub-sub-task doesn’t inherit the custom fields, any reason why?
That’s just the design of Asana, I’m afraid - custom fields only inherit one level down from a project where they’re added to.
You can get them to show on a sub-sub-task if you attach the subtask to the project. However, that has some side-effects, the most significant of which is discussed here.