The business requirement is, only approver(vp) can reject or approve the records and other users like marketing,qard,buyer,labelling can modify records. 
Approver(vp) cannot modify records and other users cannot approve/reject records.
So we need to hide 'Modify' option for approver(vp) and 'Review' option for other users. 
 

Hide Review and Modify options depending upon the logged user when workitem created.

ALL

-Create customInit.html file in 'Enterprise folder' under 'htmlprops',if it doesn't exist.
-Open that file and write below code:

<script type="text/javascript">

function customInit()
{

var ename=document.getElementById('ENTERPRISE_USER_NAME').value;

if(ename == 'marketing'|| ename == 'qard' || ename == 'buyer' || ename == 'labelling' || ename == 'vp')
{
    if(ename == 'vp')
    {
            var divModify = document.getElementById('MAINPRODUCTEDITLINK');
                        divModify.style.display='none';
    }
    else
    {
    
    var divReview = document.getElementById('MAINREJECTIONEDITLINK');
                        divReview.style.display='none';
    }

}

}
</script>

-save the above file and just refresh the page. It will automatically reflect the changes.

Note:
Using customInit.html we can customize the MDM UI. 

 MDM Boot Camp in that unit 19 record UI,Lab P Custom UI and Javascript tutorials