What changed in that fiddle?
The radio boxes aren't working so I fixed them.
The functionality of the form fields requiring text still doesn't work 100%, if you write something in all 3 fields, it enables the button and then delete the text from one of them, it still keeps the continue button enabled.
But the button code doesn't work now. If you click the button when it's enabled, it doesn't hide/show the elements.
<button id='stage1' onclick="hide('foo');show('bar');update();">Continue</button>
Sorry if I'm not being clear. I'll have a closer look tonight.