delete all match

1) How do I delete all songs from iTunes Match? The instructions that I've followed so far: open Itunes. Turn on Match. Select all songs that have a cloud with a downward arrow, right click, delete. That gets rid of them from my library on my desktop computer, but they're still on all my iOS devices. Does that mean they're not really gone?

2) I wish there were a way to edit only those songs stored on iTunes Match...is there?