It seems to be 2 version "Standard version and Advanced version" Polycom Sweden person says that the standard version are the same functionality as the c100 client so you don't need a CMA registration, only for more features.
That is correct, there is only one download version. Registering to a CMA server unlocks advanced features such as Content.
Yes, the RealPresence Mobile can run as a stand alone H.323 client. You may dial another tablet or endpoint by entering the IP address and pressing call. If you want to dial by extension you can point the app to the CMA as the gatekeeper.