This feature is available in Catalyst, Enterprise, and Ultimate editions.
Yes, but the part of the CommitStream process relies on a secure, remote service. If the configuration of your version control system and network allow HTTP traffic to reach the CommitStream service hosted outside of your network (https://commitstream.v1host.com) you can use an On-Premise (Local) version control solution. This also assumes that the connector code for the communication between your local SCM and CommitStream has been written and published.
See to Using CommitStream for more information.