The foam is much firmer than what you would find stock in a case.
Yes, if you pinch it very hard, it will crush. That's the nature of foam, But spring back is slower than your avg. couch cushion spring back. So it will slowly come back to size. But it will come back to size! This helps out with temporary placement and eventually permanent placement.So as far as your last questions, it depends on how long the item has been comporessed in the foam.