Hi Ninad,
you have simply to configure which checks should be executed during the "approval" WF step:
- go to MDGIMG -> Process Modeling -> Change Requests -> Configure Properties for Change Request Steps
- select your CR type
- on the left column, click "Change Request Step"
- select the desired WF step
- on the left column, click "Enhancements and Checks per Change Request Step"
- for the validation "Duplicate Check" select the execution option "Always Executed"
BR,
Riccardo