We are planning to migrate an application built on Pega 8.3 and PegaGP 8.3 to Cosmos. We have removed the UIKit from the application stack and replaced it with Theme-Cosmos application. However, it is being referenced from the PegaGP(Government platform) app. So the UI is still not fully reflecting Cosmos. So I would like to know if it is possible to upgrade an application without the underlying framework upgraded to Cosmos.