1. It should be deleted - as far as i can remember - as long as the you dont move the device in a container witch is not synced. I´m afraid i can´t answer the 2 question - never tried that.
On #2, that is not possible. If would have to be an offline process. But as a workaround, use a server task do delete managed systems that have been inactive for more than x day (30 for example)