Any particular reason you are creating multiple implementations?
Pega already has ootb api to create case from one application to a different application, this should be utilised in-your case. If you don’t want to do this, then you can make an entry to a common table and have an agent parse the records and create cases
I am not sure about the exact Pega minor version , you can check the application URL alias in the application definition rule. I believe you can use the that URL to work on different application cases without changing the application definition rules. Refer to the screen shot atttached.