Before a flow is deployed to an environment, it is stored as a draft. Only users from your organization will have access.
All revisions are automatically saved.
To find all the previous versions of a flow, first click the Saved [.. minutes] ago ... tab on the right side of the flow editor.
In order to revert to a previous version, identify the version you would like to revert to and then, in the dropdown for the particular revision, select Revert.