I believe you can simplify your formula by only using ISACTUALVERSION() formatted as a boolean. You must remember, Current Period is defined from the Time Settings (in my reply to your previous post).
Which Version to display is deremined by the Switch Over date in Versions as well as if you are using Swicthover at the line item level.
So, using the above parameters and creating a module Time by Version, the checks will render the actual data.
The Version will still show Budget or Plan, but the data will be from the version Actual and will not be editable.
Since Versions can be named anything, Anaplan doesn't have a function for IsBudgetVersion or IsPlanVersion. With that said, you can use the Formula Scope in the blueprint to help writing formulas for All Versions (which is likely what you have specified since it is the default), Actual Version, All Versions except except Actual, as well as the Current Version (define in the Version Settings).
If you would like to know which months are not Actual, you can use the following formula: NOT IsActualVersion()
If you would like to know when the switchover date is for a certain version, you can figure it with this formula:
IF NOT ISACTUALVERSION() AND ISBLANK(PREVIOUS(SwithOver Period)) THEN ITEM(Time) ELSE PREVIOUS(SwithOver Period) which is formatted at Period - Month.