I'm trying to change the thread tags on a bunch of posts that I want to move to an archive, it's not working, it'll change a couple of them, but not all the ones I've selected.
Interesting. Just so I know, what browser are you using?
Also I want to move the applicants that have been accepted to an archive in a different group under officers, is there a way to do that?
Automatically, not currently. You'll have to move the thread tags manually.
That said, it's not a bad idea to add the ability to change thread tags automatically for archived apps.