Hi

We did implement similar solution last year in our organization. We made RPA Pega instance as enterprise solution so that any other regular BPM or CS solution can interact with it. We used Pega API to establish communication between Pega BPM/CS instance with RPA instance. We created a case in RPA instance when Pega BPM process reaches a stage which needs robotic automation to execute. In the case life cycle of RPA automation will be present. Upon completion of automation status will be shared through API to Pega from Robo manager. Until it receives status from RM Pega case will be in a wait shape. We are storing CaseIDs of Robo Manager in Pega and Pega Case ID in Robo Manager. So that all further communications will happen through get/put methods of Pega API. In this way not only a Pega app any other application other than Pega can also use Robo manager RPA solution as a service. 

On the question of version differences - Yes. We do have different versions for Pega and RM. As described earlier since we are communicating with Pega REST API it's a very loosely coupled system with very minimum dependency.