Form will have data part andapproval part with Comments and Approve /Reject.
When the rejected forms back,the comment box and buttons should appear(multiple times).
@Soji I'm not sure I understand what you're saying here.
In order for the form to have buttons for approval and comments area, you have to design this, unless you are using the task form which is predesigned out of the box.
Can you help us understand what you're trying to achieve?