They should work and compatible if it’s not too complex (content and composition of the site). I’m just saying that issues may appear depending on your existing setup from those old versions. That’s why we recommend doing it on staging and it’s a common practice, but I’m not forcing you to do that , it’s just my personal recommendation.
WPBakery is a visual composer, I just mentioned it in case the shortcode you’re seeing is from them.
As for the endpoint, we did provide and it’s available from your forum dashboard and they are STABILITY RELEASE versions. But since you’re coming from very old versions, some Major differences are unavoidable. We did add backward compatibility but of course, just to give time for transitions so users will not be forced, but it’s not permanent and has to go (for allotted time) for security and performance. Even PHP and Wordpress have deprecated features that break theme and plugins, so the rest should follow including our theme and plugins.
Back to the issue, what shortcodes you’re seeing? Though, it will be harder to troubleshoot since you don’t have a working copy as you didn’t use a staging that we could use for comparison.