I found a workaround for this issue.

Once the modal has been hidden bootstrap data still remains on it. To prevent that I had the following:

$('#myModal').modal('show'); //display something
//...

// if you don't want to lose the reference to previous backdrop
$('#myModal').modal('hide'); 
$('#myModal').data('bs.modal',null); // this clears the BS modal data
//...

// now works as you would expect
$('#myModal').modal({backdrop:'static', keyboard:false});

you can try passing in the backdrop option into the modal method

j$('#apvideo').modal({backdrop:'static'});

check the bootstrap modal reference for all the available options

data-backdrop is used to Specify static for a backdrop, if you don’t want the modal to be closed when the user clicks outside of the modal. and backdrop Specifies whether the modal should have a dark overlay:

• true - dark overlay
• false - no overlay (transparent)

If you specify the value "static", it is not possible to close the modal when clicking outside of it

put this script inside your code, pass your modal id into it

$('#myModal').modal({
          backdrop: false
        });

Here is the snippet

$(document).ready(function(){
    $("#myBtn").click(function(){
        $("#myModal").modal({backdrop: true});
    });
    $("#myBtn2").click(function(){
        $("#myModal2").modal({backdrop: false});
    });
    $("#myBtn3").click(function(){
        $("#myModal3").modal({backdrop: "static"});
    });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://netdna.bootstrapcdn.com/bootstrap/3.1.1/js/bootstrap.min.js"></script>
<link href="https://netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css" rel="stylesheet"/>

<div class="container">
  <h2>Modal Options</h2>
  <p>The backdrop option specifies whether the modal should have a dark overlay (the background color of the current page) or not.</p>
  <!-- Trigger the modal with a button -->
  <button type="button" class="btn btn-info btn-md" id="myBtn">Modal with Overlay (backdrop:true)</button>
  <button type="button" class="btn btn-info btn-md" id="myBtn2">Modal without Overlay (backdrop:false)</button>
  <button type="button" class="btn btn-info btn-md" id="myBtn3">Modal with backdrop:"static"</button>

  <!-- Modal -->
  <div class="modal fade" id="myModal" role="dialog">
    <div class="modal-dialog">
    
      <!-- Modal content-->
      <div class="modal-content">
        <div class="modal-header">
          <button type="button" class="close" data-dismiss="modal">&times;</button>
          <h4 class="modal-title">Modal with Dark Overlay</h4>
        </div>
        <div class="modal-body">
          <p>This modal has a dark overlay.</p>
        </div>
        <div class="modal-footer">
          <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
        </div>
      </div>
      
    </div>
  </div>
  
  <!-- Modal -->
  <div class="modal fade" id="myModal2" role="dialog">
    <div class="modal-dialog">
    
      <!-- Modal content-->
      <div class="modal-content">
        <div class="modal-header">
          <button type="button" class="close" data-dismiss="modal">×</button>
          <h4 class="modal-title">Modal without Overlay</h4>
        </div>
        <div class="modal-body">
          <p>This modal has no overlay.</p>
          <p><strong>Note:</strong> You cannot click outside of this modal to close it.</p>
        </div>
        <div class="modal-footer">
          <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
        </div>
      </div>
      
    </div>
  </div>
  
  <!-- Modal -->
  <div class="modal fade" id="myModal3" role="dialog">
    <div class="modal-dialog">
    
      <!-- Modal content-->
      <div class="modal-content">
        <div class="modal-header">
          <button type="button" class="close" data-dismiss="modal">×</button>
          <h4 class="modal-title">Static Backdrop</h4>
        </div>
        <div class="modal-body">
          <p>You cannot click outside of this modal to close it.</p>
        </div>
        <div class="modal-footer">
          <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
        </div>
      </div>
      
    </div>
  </div>
</div>

As per Bootstrap docs:

Clicking on the modal “backdrop” will automatically close the modal.

When backdrop is set to static, the modal will not close when clicking outside it.

Via JS:

$('#myModal').modal({
    backdrop: 'static',
    keyboard: false
})

$('#myModal').modal({backdrop: 'static', keyboard: false}, 'show');

Via HTML:

<a data-controls-modal="your_div_id" data-backdrop="static" data-keyboard="false" href="#">

On Options chapter, in the page you linked, you can see the backdrop option. Passing this option with value 'static' will prevent closing the modal.
As @PedroVagner pointed on comments, you also can pass {keyboard: false} to prevent closing the modal by pressing Esc.

If you opening the modal by js use:

$('#myModal').modal({backdrop: 'static', keyboard: false})  

If you are using data attributes, use:

 <button data-target="#myModal" data-toggle="modal" data-backdrop="static" data-keyboard="false">
    Launch demo modal
 </button>`

Hi @anonymouse703

Which version of Bootstrap are you using?

Try replacing
data-backdrop="static" data-keyboard="false"

with
data-bs-backdrop="static" data-bs-keyboard="false"

post Bootstrap v5, we have to use data-bs-*

Ok I solved this. Maybe it is not the best solution, but it is working for my special case.

I added $('#myModal').off('click'); just after I show loading spinner on submit. This prevents from closing modal with mouse click.

There was a problem with disabling escape button, because browsers stops page loading when user press this button. So I decided to hide the spinner to unlock the form with this code:

$(document).on('keydown',function(e) {
  if (e.keyCode == 27) {
    $('#myLoadingSpinner').hide();
  }
});

Edit: I found another solution for backdrop:

$('#myModal').data('bs.modal').options.backdrop = 'static';

I tried this also for keyboard = false, but it doesn't work.