No problem, happy to clarify these things before you purchase :)
1. Yes, there is a setting in the JobRoller admin dashboard which allows you to determine who can access the resumes page as shown here on the
JobRoller admin demo "Resumes" tab under "Resume Options". You also have the option to charge to view resumes if you wish.
2. You can create child/sub categories within the admin dashboard, so this can be selected when the job listing is placed. The "Browse By" Filter on the sidebar doesn't show the child category on the main page, only when you select the parent category first (then you'll see the child categories displayed underneath in the sidebar).
3. There is no invitation option as described, so this would require customization.
4. This really depends on how you set things up, so it's probably a good idea to research the options/considerations
here. Thanks :)