If you right-click in your repository root and select Tortoise Git
-> Diff with previous version
you can see the differences between versions. Click the down arrow on the RefBrowse buttons and select Log from the popup menu to access the commit log for both versions. That will allow you to go through the project history and choose revisions from the past.
You can see what files have changed in the lower part of the screen and then right-click on individual files and show individual changes between versions.