Otherwise, old and new git interact really quite well. You'll miss out on new features, naturally. Because of reasons, I still make daily use of 1.8.2.2 and it's fine! (but only when interacting with trusted peers within my organization, that thing hasn't seen a security patch in a decade or so)

As for release notes, every release gets its own file here: https://github.com/git/git/tree/master/Documentation/RelNote... -- you'll get the highlights of major features by reading the x.y.0 release notes.

Git is not a hard build from source as such things go, but it leaves you to track security fixes on your own.