It is not suggested to have 2 different production applications(FCCS,PBCS) in test and prod.
Your approch will violate the guidelines.
If your subscription includes both FCCS and PBCS I think you should be able to have both applications in both pods.
I know that but I want to use the PBCS test instance for preparing FCCS Demo for a few days only.
After that, I will migrate the snapshot from prod instance.
Just want to know the consequences if any.
I have the subscription for PBCS application only.