Hide next/submit button at end of survey

You can do this using JavaScript. On the last question go to the Advanced Question Options -> Add JavaScript. Delete out all the existing code and add the following:

Note that I'm displaying the message as an alert for simplicity but you could create a custom error message at that point. Hopefully this puts you on the right track.

Qualtrics.SurveyEngine.addOnload(function()
{
/*Place your JavaScript here to run when the page loads*/
//disables the next button on the page
this.disableNextButton();
//question click is a simple onclick handler
//attached to the question's container div
this.questionclick = function(event,element)
{
//by default you get the click event as the first parameter and the clicked element as the second parameter
console.log(event, element);
if (element.type == 'radio')
{
var choiceNum = element.id.split('~')[2];
if (choiceNum == 1)
{
//enables the next button - Note that the QuestionData object is bound to this to make it easier to use
this.enableNextButton();
}
else
{
//alert
alert('Please ensure that all applicable questions have been answered');
//disables the next button
this.disableNextButton();
}
}
}

});

Qualtrics.SurveyEngine.addOnReady(function()
{
/*Place your JavaScript here to run when the page is fully displayed*/

});

Qualtrics.SurveyEngine.addOnUnload(function()
{
/*Place your JavaScript here to run when the page is unloaded*/

});