Your route should be 3.5 first (because you can't take 3.4 to 4), then the latest version of 4, then the target version of 5.
The release notes you need to follow are "all of them". Skim the point releases, they're all bug fixes or tweaks and unlikely to be of any interest unless you've specfically hit a bug in there. But you'll want to read the notes for 4.0, 4.1, 4.2 etc. Concentrate on the releases you actually need to implement obviously, but you need to read all of them to make sure there's nothing that will bite you.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.