If you're using the import and export tools within Kentico, you cannot go backwards in versions or hotfixes. This is very common in most any software. You can however, import/export from an older version into a newer version in most cases.
There is an import tool included with the Ultimate version of Kentico in where you can connect one datasource with the Kentico database in import objects. I'd suggest looking at this tool.
Or if you are ONLY using a Custom Table, you could manually create the structure within the Kentico UI and then run MS SQL data import and import the rows into that custom table. I DO NOT recommend this for anything else besides custom table data simply because of the dependencies for other objects that will need to be created that you won't get when using the API tools.