Some IOS support an archiving feature, which I believe, can save revised configuration changes. However, it's off, by default (or at least that was the default).
Many devices, as part of the forgoing, can do a UNIX like "diff" between a saved configuration and running configuration. This will highlight all the existing differences between those configurations, but unless no one has "saved" the running configuration for the "last 3 years" you won't be able to see all that's been changed.
The forgoing applies to L3 switch itself, but if anyone has been saving device configurations, external to the device itself (a good thing to do), you might be able to use a "diff" utility and highlight changes.
