A new try.
I managed to save the VIFRAME in build 4686 and open it in 4881.
Don't ask me why, but in my configuration, Play works ( and you can also interact with its GUI under VE Pro) only if you are loading a VIFRAME saved with the previous version (in this case, 4686).
So that incompatibility seems to be even more strange than it appeared before!
Scenario 1: loading into 4881 a VIFRAME created in version 4686 ends to a completely working environment: you can both play the instruments and interact with Play's GUI (even if the VE Pro audio engine button is switched off and the VIFRAME has been saved for changes in version 4881)
Scenario 2: loading into 4881 a VIFRAME created in version 4881 ends to a not interacting GUI and you cannot do anything with Play.