Spliting topic into an obviously new topic.
The SVN commit number to version was a recent addition to the change log. It allows us to beter retrieve a secific version from the SVN, or compare code between the two.
However individual changes are often either part of a large set of changes, or sometimes spread over a number of commits as such the commits between the versions do not always represent specific changes. For that you will need to compare code between revisions.
SVN has ability to retrieve files for specific commits ('svn cat') and list the version numbers in which a specific file was updated ('svn log') and get differences ('svn diff'). I try to include appropriate log messages for most on my commits other than the most minor ones, but that is me.
However I tend to find using these low level command slow and annoying...
For comparing between versions or current version an specific version (or the HEAD if others have since committed), I like to use the python program "diffuse". This is SVN savvy, and will show the changes (includeing small character by character change) between two files, or svn revision(s). The display is side-by-side, using colors to show changes, and can even bring up more than two files/revisions at the same time!
For example... I use this command regualrly to see recent changes in the IMv6 command line API.
To see whcih files in my svn is out of date I quite often use
svn status -u | grep '\*'