Thanks for writing in! Most users rush to the updates and then if it does not work, tend to get frustrated which of course we always understand it especially if you are on a deadline. Before you update, we highly recommend that you always set up a staging area. This is very useful because you can test drive any X updates in the staging area, do the customizations and troubleshooting without disrupting your live site. Once everything is perfect, you can easily and flawlessly proceed the update in the live site. To know how to create a staging area, please check out these articles:
Now, after doing the updates, you also experienced issue like Cornerstone no longer working. It has worked before the updated and after doing so, it does not work anymore. One of the major cause of this issue is caching:
You have have installed WP Super cache, W3 Total Cache or any other caching plugin. You must always clear your plugin cache right after the updates or slight site changes.
Other users are using minify plugins or applied minification for the JS and CSS. Well you will need to regenerate the minified JS/CSS files first after doing the updates.
If you are using CloudFlare, you must purge your site cache too.
If you are using WPEngine or Site Ground, there is a caching feature in the server which you will have to clear the site cache too.
If you are on BlueHost, they have Endurance Cache which could also pose a problem if the cache is not clear.
Other servers has Varnish. The Varnish cache must be cleared too.
Hope this helps.