'Edit to' and 'Edit from' is the best option to restrict the data feed into the specific versions. It should work.
But if it not working out, your can use the dynamic cell access as well. Create a module with a 2 boolean line items with the versions and use it as a Read/Write access driver. Whenever required you can lock the specific time periods for any version you want.
The import action will let you to import the data in all the cells if you have an administrator access of that particular model/workspace irrespective of the periods set in 'Edit From' and 'Edit to'. Once your admin access is disabled (like the end users) you can only import the data in the selected period only as set in 'Edit From' and 'Edit to' fields. The same goes with the Dynamic Cell access as well.
@tompatrickting22 As mentioned by @anand.shekhawat ideally you cannot restrict data updates via import. However if you really want the import to lock the Actuals data, I would create a transactional module as a temp module to load all the data via import from the source, then create a saved view with filters to show only forecast months and use this saved view to import into the main module wherein you want to lock actuals.