Roles and permissions

Hello,

I am currently customising my Moodle roles and have the following queries:

1. Confirmation that a teacher in 1 course may not access a course of another teacher's whilst in the same category.
2. My teacher roles have the ability to show/hide courses (and still see them). If the teacher is not allocated to a course, does that mean they can still see the hidden courses of the category?
3. .....and say i want to create an "Archive"  category and hide it. Will the teachers be able to access and enter the categories and courses?

Thanks a lot, Leticia