Angular is the successor to AngularJS. We always train the latest version. At the moment this is version 5.
If so-called breaking changes occur during the further development of the framework, this will only be published with the next major release. Thus, the compatibility can be read in an update directly to the version number. The cracking changes in the version jump between 2 and 4 did not have any implications for most developers. This procedure ensures better planning of your applications.