Neither Process Builder or VisualFlow record the package version that was used when an invocable method is referenced. Thus, it is not possible to perform behavior versioning. System.requestVersion returns the currently installed package version. The definition of the invocable method is controlled by the constraints relating to the use of the global modifier, as we have already discussed in this chapter. As a best practice, avoid adding new required members (via @InvocableVariable) to your parameter classes.