That's why I don't rush to install new browser versions: first, I spend some time studying what people are writing about the changes and new features, and how other users are reacting to them. It's especially undesirable to use automatic updates. There's also a simple solution: for example, I save the current browser version when I download and install a new one. If something goes wrong, I can always revert to the old version.
As for bookmarks in browsers: everywhere there are export/import functions, and I recommend periodically exporting bookmarks to an HTML file and storing it in a specific location. Then you can be sure that important pages won't be lost if something "terrible" happens. You can also open such a file in a browser at any time and find the page you need: for example, I have Firefox and Opera, and when I was using Opera, I had a lot of bookmarks in it; but now in Firefox, I haven't added almost any pages to bookmarks: the history and smart address bar help me get to the desired site by typing only 2-3 letters!