Hi Karthik,
Create an enumeration for approval and reject. In a microflow, create an change activity select your entity and click new select your enum and in value provide as (Yourmodulename.enum.approval) I have added the image for your reference. Same applies for rejection also and add the show page activity. In newly created pop up page add a text area to mention the reason and give the access rules to admin.
Hope this helps!!!
Hi Karthik, try creating two buttons one for accept and reject.
On click on accept just change the enum value to approve and on click of reject call for a page which takes in the comment and on save of that change the enum value to reject.
And to show them in a different page, create overview pages and based on the enum value of particular records give xpath as Accept and Reject.
This should solve your problem