Whenever a bug is fixed or a change is made to the code a new version of the latest code becomes available at http://nopcommerce.codeplex.com/SourceControl/list/changesets which includes all the fixes applied till date. you can download it and compile it to check the solutions. A new version like 2.4 would contain all the fixes plus the release is tested rigorously to be called a stable release. A changeset is not recommended to be used in a production environment although its pretty much is the same as the stable release just not tested end to end.