We say we require Mac OS 10.7 and above, because Avid says they only support ProTools 10 on 10.7 and above. I didn't know that you could install and run ProTools 10 on Snow Leopard without any problems.
In any case there isn't any difference between the demo version of our software and the purchased version. So, if the demo is working, then the purchased version will work the same. But I'd take my time if I was you and spend a week or two checking everything out though. Band Delays for instance uses a different technology for its UI than the other plugins; so you might want to double check that that plugin is working fine on Snow Leopard. Also, the offline bounce feature in ProTools has been problematic on some versions of OS X. So, you might want to double check that that feature is working as well.