Do I need Captcha in Unity?

Do you need it, not really, however if you would like to add one just download a captcha picture and put it where you want it and add a small invisible button on the box. You could probably also add a check that appears or moves from outside your vision to the desired cord, then make an if statement or something to check if the button is pressed and if it equals true spawn or enable a button (I know this isn't very helpful but it's the best I've got)