Nothing has changed with the plugin (there were no recent updates and this is NOT a “new” behavior for it), so if you just updated it 2 weeks ago, you must have been using a very old version. With that in mind, is the rest of your site up to date? And what other code did you update at the same time? The plugin itself does NOT strip HTML but many other things can, including filters set up in your theme functions file, user preferences/permissions controls, etc. which can strip HTML on output or prevent it being saved to the database to start with.
As far as versioning goes, there are 2 older versions of the plugin in the WP repository, which are easily accessed thru the plugin’s WP page from the “developer” tab but I wouldn’t recommend using either one with the current version of WP. And your own backup files should also include earlier versions of anything on your site, including the plugin files and the database entry for your original instructions (before you edited them) with the related HTML.
If you mean “versions” like how a post can save multiple versions of its content – this is a plugin and when you change the settings, including what will display in the widget, you are NOT editing a post and don’t have the ability to use all the extra fields and settings available to posts, including having multiple versions of the post content. I don’t think anything in WP saves multiple versions of settings in the options table; the options table doesn’t include date stamps so WP wouldn’t know which version of the settings should be loaded. And having the plugin create a custom database table and including the code to use that instead of the regular options database table, simply to “version” the content of a single metabox would bloat the code for little reason. If you have long instructions that require a lot of HTML, don’t use the plugin for that – make them posts instead, put them into a special “help” category, tell your theme not to display anything in that category unless the user is logged in, then use the plugin – with some very short text and a link – to tell your logged-in users how to access that archive.
