You could do so, but it's actually meant for when a certain setting (like physics or edit-mode changes) has some serious effect on your content (as when it would make it incompatible).
If that's not the case, don't do so.

You should be fine. Backwards compatibility is generally very well maintained. It's just when you start using features from a newer version that you should indicate it. SVN may not work perfect with the current release, but content from the previous releases should. There are exceptions, but they are generally for content from a REALLY long time back.