Thanx for your reply...!!
Let me explain it more appropriately. I am making my app (let's say- MYAPP) in company environment (Note: I am not in IT system administrator). This app is shared with everyone in our company environment. Anyone from our company environment can fill up the form in powerapp with a sharepoint data source.
Once the form is filled up, it has to be rated by people in a specific department (say CORP) of our company.
Your reply has given me one idea- To create 2nd app using the same data source and share it with the CORP people only (dis will restrict other users to view/modify). Once any form is filled, using microsoft flow it will notify the CORP people and they will visit the 2nd app and give the ratings which will be updated in sharepoint.
Is there any way of doing it in same app??