Modal pop up cross button on top goes under the title bar

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ASP.NET

jQuery

Here is the modal pop up that opens an aspx page in dialog

$("#dialog_test1").load("Test.aspx", function () {
        
        $(this).dialog({
            autoOpen: true,
            modal: true,
            resizable: false,
            draggable:false,
            width: 680,
            open:function()
            {
                $('#tabslist').tabs({
                    create: function (e, ui) {
                        $('#closeBtn').click(function () {
                            $('#dialog_test1').dialog('close');
                        });
                    }
                });
              
            }
        
           
                 });
        $(this).siblings('.ui-dialog-titlebar').remove();
        $(this).css('height', 'auto');

    });

I am trying to remove the title bar and have my close X buttom on top right corner

And that's my tab controls in an ASPX page which opens in dialog

<div id="tabslist">
        <ul class="tabs-menu" style="list-style-type: none;" >
            <li class="active" style="list-style:none;outline:none; " ><a class="anchor" id="TabInfo" href="#TabInfo" style="text-decoration: none;" >Information</a></li>
            <li style="list-style:none;outline:none; "><a class="anchor" id="Tab1" href="#Tab" style="text-decoration: none;">Tabdetails</a></li>
             <li class="tabs-close-button"><button id="closeBtn">X</button></li>
          
            
        </ul>
    </div>

What I have tried:

I tried to hide and remove, but none of those work and my cross button is under the title bar. I placed style on cross button z-index but it is under the title bar. Now two bugs are hanging here....
I want the title bar to go away so my cross close button is visible properly.
And also on clicking the Cross button, it throws me an error .tabs()is not a function and it doesn't close the dialog. And I know I am at old version of Jquery 1.6 but how do make my close button click work