Hi @cheezitman,
Multisite: yes, it supports, but not per site. The admin moves into the Network Admin if used in multisite install.
For BuddyPress, that’s another question; I would not really recommend caching with BuddyPress this way. Object cache and persistent caches; maybe database cache ( better if on the DB side itself ), but full page cache on a community site is dangerous in my opinion.
If really needed, put the inactivation time to 1, or 2 seconds at max, doing a micro-caching. This saves from an agressive load, but does not cripple the site’s update possibility at total.