How do I know if someone has read my application for something and how do I see the threads I have sent also relating back to the first question do I get a notification or something to tell me if some has replied or seen it?

If you mean for a staff application, the staff team will reach out to you if you're accepted. If not then you either didn't get accepted or they aren't looking for staff.
You can see threads you've posted by going to your profile and clicking the "Threads" tab.