@kishan1 In order to restart a specific processor group you will need to use some command line magic against the Nifi API. For example, this could be done by using a command to stop the processor group, then the restart nifi command, then start processor group. You can certainly be creative in how you handle that approache once you have experimented with the API.
https://nifi.apache.org/docs/nifi-docs/rest-api/index.html