Versioned to unversioned: How to undo edits in an edit session on an unregistered table
The best resource I've come across to provide an answer is Esri's Not registered as versioned or unregistering data as versioned
There are no ways I'm aware of redoing/undoing edits in unregistered tables. However, this resource provides further insight as to possibly finding a solution.
....As mentioned above, your data is initially not registered as versioned. If it remains in this state, you can perform nonversioned edits, and you can create a topology, network dataset, or geometric network.
If you've already registered a feature class as versioned and need to perform one of the above operations, you must unregister the feature class as versioned. When you unregister a feature class, the delta tables are dropped from the database—that means all versioned edits that were made but not posted will be lost. To prevent these edits from being lost, either compress all the edits to the base table before unregistering the data or compress them to the DEFAULT version from the Unregister As Versioned dialog box. The software prompts you to compress the edits to the base table when you attempt to unregister a feature class as versioned.
You can access the Unregister As Versioned command from the dataset context menu.
To avoid the need to unregister feature classes, try to apply all topology, network dataset, and geometric network behavior to your geodatabase before you register data. Test the topology, network dataset, and geometric network in a file geodatabase or on a development server to ensure that you are not missing any rules. This can save you from having to unregister feature classes later in production.
ESRI's GeoDatabase versioning, must be enabled for the ArcGIS/ArcEditor smart data editing tools to be enabled. Whether you need to use versioning or not is immaterial: if you want the smart editing tools you have to use it, otherwise you have to revert to standard SQL transactional editing.
I don't have a problem with that approach as there is probably a deep architectural and functional integration through the ESRI stack which makes it difficult to enable only one element.
Or questioner doesn't appear to want or need long transactions (crossing multiple days) or multiple versions (per user or per a group of editors). They simply need to all the user to create multiple versions within a single session and, before committing their edits, chose the one they want.
For GIS people, with GIS front-end software (qGIS, ESRI, Autodesk, MapInfo etc) there is little available. Mainly because of the lack of a consistent API with underlying database management (SQL based) from the main database players.
Oracle provides Workspace Manager which is supported by Autodesk and ESRI; Microsoft's new Temporal Tables has no GIS vendor support that I know of.
If the capabilities of Oracle's WorkSpace Manager and ESRI's GeoDatabase versioning are a universal requirement for GIS people, then we would have seen standardisation or an open source project (eg GeoServer, PostGIS, etc etc) that promoted a cross-database solution: but we have not.
Finally, one issue I have with ESRI's Versioned GeoDatabasee is the lack of availability of a "current view" capability. That is, the database itself should provide any user/application that accesses the GeoDatabase a consistent view of the data at the current point in time. From what I understand user versions are kept in delta tables with reconciliation only back to the base when requested. I have heard of customer sites where the commit back to base had never happened with the current version in the main table being long out of date.
One of ESRI's weaknesses appears to be understanding that their GeoDatabase should make all the data it manages (eg code tables) publically available to all clients and not just their own. And that often a GeoDatabase should be capable of being configured to work with a pre-existing database model (and not have to build it from scratch using ESRI GeoDatabase design tools).
If I have mischaracterised what ESRI GeoDatabase does, please let me know.