Hi @sagars
I have written a code snippet for you that should work.
To allow your multifield to add item to top, follow these steps:
1. Add granite:id property to your multifield node with value "multifield-custom-insert-first". That should look like this:

2. Create clientlib with category "cq.authoring.dialog" and add the below JS code to it.
(function(document, $) {
"use strict";
$(document).on("dialog-ready", function() {
var MULTIFIELD_CUSTOM_FIRST_ID = "multifield-custom-insert-first";
var multifieldCustomItemsCount = 0;
var customMultifield = $('#' + MULTIFIELD_CUSTOM_FIRST_ID);
if (customMultifield.length) {
multifieldCustomItemsCount = customMultifield[0].items.length;
}
$('#' + MULTIFIELD_CUSTOM_FIRST_ID).on("change", function(event) {
if(event.target.id == MULTIFIELD_CUSTOM_FIRST_ID){
if(event.target.items.length != 1 && event.target.items.length > multifieldCustomItemsCount){
event.target.insertBefore(event.target.items.last(), event.target.items.first());
multifieldCustomItemsCount = event.target.items.length;
}
}
});
});
})(document, Granite.$);
Try this and let me know.
Hope it helps!
Thanks,
Nupur