There are many functions available for managing your Project Revisions.
In the Project Explorer, select the Project that you want to view/manage the Revisions for and click the Revisions tab in the bottom section of the interface.The Revisions tab displays all of the previous Revisions for a Project.
From here you can Create a new Revision for the Project, open a Revision (read-only), Compare Revisions, edit Notes on existing Revisions, delete, rename, and even export the list of Revisions to Excel. You can create a Project based off of a Revision via the Clone as Project function. You can also choose to promote a previous Revision back to be the current (editable) Project via the [Promote as Project] button.
This will allow you to rename a Revision. You should never manually rename files in SI, always use the Rename function.
The Promote as Project feature allows you promote or restore a previous Revision to be the current Revision. This is useful for when you present Revision to a Client and they prefer a previous option that was presented. This will save the time of manually undoing all of the changes in the current Revision.
This is the safest option, when you choose this, the current Project will be saved as a Revision and the Revision you selected will be copied to be the "current" Revision. Use this when you don't want to overwrite the "current" Revision and would rather it be added to your Revision list in case you ever want to review it.
This will copy the Revision you've selected and replace the "current" Revision. Use this if you don't want to keep a record of what changes took place in the "current" project.