Turn OFF Autoadvance option for last question in survey

That won’t be possible. Autoadvance is all or nothing. 

You could probably implement autoadvance manually for some questions like this:

Qualtrics.SurveyEngine.addOnReady(function () {
	const quest = this;
	const qc = quest.getQuestionContainer();

	const allInputs = qc.querySelectorAll("input");

	allInputs[1].oninput = function () {
		quest.clickNextButton();
	};
});