I have discovered a master solution for Calls to Return to Source Extension if not Answered on Transfer.
1. Create a Group for each extensions that you want calls to return from if not answered.
2. On Fail Over destination, select the Source Extension which will be transferring calls then save and apply settings.
3. On each phone, login direction using its IP address, Go to Ring settings, Set Ringing time to how many rings you want before the calls are returned back to the source.
Save and Apply.