That’s correct. We are trying to keep the GVM-10 release page up to date.
Because you are comparing different things. The master branch always contains the newest development branch. Currently master has been updated to contain the next next version for GVM 20.04 which will be called gvmd 20.04.
Not yet. But it will be released in the next weeks. See this post for some background about our release schedules. An up to date version of our release schedule can be found here. See this topic for a map of GOS to GVM versions.
Personally I would tend to say no. We renamed a lot of components and got a complete new GSA (our web application). A short list of notable changes can be found at the initial release announcement.