It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

Say I released 3 of 4 ghosts in scenario. Now, when I replay scenario they are all there again so if I release just the one I missed earlier and ignore the others will I lose the other three?
This question / problem has been solved by vv221image
Once you unlocked a ghost, it’s with you forever ;)

No problem with unlocking them in multiple sessions, the only reason to get them all at once would be to reach the higher scores.
Indeed. Managed to found out myself in the meantime.