Question

How to test if an element resides in an iFrame using jQuery and if it does, how to select that iFrame?

Answer 1

Try this it will work for you.

var requiredIframe;
$("iframe").each(function(){
  if($(this).contents().find("elementYouAreLookingFor").length){
     requiredIframe = $(this);
     return false;
  }
});