I can't remember what the other platform options are, but for VSCode you need to use a preview version, which has meant I haven't had much time to test it yet as I'm full on with the stable release.
But as an example I can select a block of code and ask it to generate tests, explain it or various other stuff. I haven't tried it further yet to see to what extent is provides value beyond just saving copying and pasting and establishing a context in ChatNormal.
It's not clear either that it is 4 as you requested; it may be the default 3.5, I've had a very brief look but couldn't see the spec.
Update, according to the Verge, its 4:
https://www.theverge.com/2023/3/22/23651456/github-copilot-x...