We are hoping to have Scrivenings functioning in the next beta release (5). It will be included in the change list when it is available. We know it’s an important feature; it’s just been giving us some trouble, and we weren’t really happy with the alternative to disabling editing being potential total text scrambling… 
Not quite–3.0 for macOS was only released at the end of last November, and the Windows beta went live at the same time. But naturally you should use the tools that will best aid your writing, whether that’s Scrivener or some other program or just a really nice set of pens. 