Change requests are necessary for any corrective actions if the baseline has been confirmed and signed off, in this situation, change request is necessary to go through the Performed Integrated Change Control (PICC) process. However, if the baseline is not confirmed, then submission of change requests are not required.
Change requests can sometimes affect the performance of the project. If the change requests affect the project performance, say in costs, then the cost of implementing that change will be documented in the change requests and should be approved by the Change Control Board (CCB) in the PICC process.