Answers for "start with a modal opened bootstrap"

bootstrap modal open event

$('#code').on('shown.bs.modal', function (e) {
  // do something...
})

bootstrap 4 start modal in modal

var modal_lv = 0;
$('.modal').on('shown.bs.modal', function (e) {
    $('.modal-backdrop:last').css('zIndex',1051+modal_lv);
    $(e.currentTarget).css('zIndex',1052+modal_lv);
    modal_lv++
});

$('.modal').on('hidden.bs.modal', function (e) {
    modal_lv--
});