If the page itself is cached, yes. You will also have to do it to any images/css/js or external files that are available via a URL on your site (assuming you are passing cache headers so they are, in fact, cached) and are contained in that page because the browser caches all available URLs and they aren't grouped together by what page called them - they are all independent. So if index.php contains an IMG then the IMG will still be called from cache even if you change index.php?v=1234. You'd have to add ?v=1234 on the image as well in order to re-fetch both the page and the image.
The version system is typically something you append to all cacheable URLs that can be modified (like css and js) but want to be invalidated as soon as it is updated. You typically append ?VERSION to the URL or ?version=VERSION to all URLs in whatever fashion makes sense (making sure not to break URL parameters).