Can't answer the first, but the second: depends. in some locations, collection is allowed, in others, it requires a collection permit. However, you don't want the sand from above the low tide area, since this will include aerobic organisms that won't tolerate full-time immersion. Also, collection is best done at areas away from the shore, in deeper water, to reduce the toxins and pollutants that concentrate in shallow waters.
Some LFS sell sand harvested from their own tanks. The pre-packaged stuff, I'm cynical that will contain much life--most organisms need access to food and oxygen, unlikely to survive for long in a bag that isn't well cared for (ie, kept cool and in the dark).