I submitted a continuation patent application. I submitted later a Continuation-In-Part patent application before getting the response from the continuation patent whose claims were rejected. Can I still respond to the continuation patent application or does the Continuation-In-Part patent application take its place? In other words, can they both co-exist and be reviewed at the same time?
They can both co-exist and be reviewed at the same time.
The continuation-in-part application contains new matter which was not supported in the parent application. Thus, you should be claiming different things in the two applications.
If the claims are not different enough (between the two applications), you may get non-statutory double patenting rejections.