JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<div class="cbb">


<select class="form-control select2 firstname v1 select2-hidden-accessible" id="name1_148" name="name[]" style="width: 100%;" data-select2-id="name1_148" tabindex="-1" aria-hidden="true">
                                        
                                        <option value="-1" selected="" disabled="" data-select2-id="299">Please Select Name</option><option value="1">K-76</option><option value="2">Af</option><option value="3">A-c</option>/option><option value="4">D-B</option><option value="5">329</option><option value="6">F-g</option><option value="7">AT</option></select>
                                        
                                        <select class="form-control select2 firstname v1 select2-hidden-accessible" id="name1_149" name="name[]" style="width: 100%;" data-select2-id="name1_148" tabindex="-1" aria-hidden="true">
                                        
                                        <option value="-1" selected="" disabled="" data-select2-id="299">Please Select Name</option><option value="1">K-76</option><option value="2">Af</option><option value="3">A-c</option>/option><option value="4">D-B</option><option value="5">329</option><option value="6">F-g</option><option value="7">AT</option></select><select class="form-control select2 firstname v1 select2-hidden-accessible" id="name1_149" name="name[]" style="width: 100%;" data-select2-id="name1_148" tabindex="-1" aria-hidden="true">
                                        
                                        <option value="-1" selected="" disabled="" data-select2-id="299">Please Select Name</option><option value="1">K-76</option><option value="2">Af</option><option value="3">A-c</option>/option><option value="4">D-B</option><option value="5">329</option><option value="6">F-g</option><option value="7">AT</option></select>
                                        
   ...

JavaScript

$( ".firstname").on('change',function() {

            
 $(".firstname option").prop("disabled", false); //enable everything

            //collect the values from selected;
            var arr = $.map(
                        $(".firstname option:selected"), function (n) {
                            return n.value;
                        }
                    );

            //disable elements
            $(".firstname option").filter(function () {
                return $.inArray($(this).val(), arr) > -1; //if value is in the array of selected values
            }).prop("disabled", true);

            //re-enable elements
            $(".firstname option").filter(function () {
                return $.inArray($(this).val(), arr) == -1; //if value is not in the array of selected values
            }).prop("disabled",false);

            $(this).prop('disabled',false);//re-enable the current one //1
            $(this).show();//and show it //1
            $(this).prop('selected',true);//just to be sure re-select the option afterwards //1
           
        });
        
        
         $('.savebtn').on('click', function(){
         $('.cbb').each(function(index, item){
         	var selectVal  = $(this).find('select').val();
                       
                        console.log(selectVal);
                        
                         });
         });