If you have set up Project history, you can view previous versions of a project and compare it against the current version.
1. Open the Product backlog or Planning view.
2. Select More > Product backlog history (in Product backlog) or More > Project history (in Planning).
The Project history dialog opens, displaying the most recent snapshot of the current project.
3. Use the Select a date in the past option to select which date you would like to view.
Dates with a corresponding project history snapshot are marked with a green highlight.
4. If the selected date contains more than one snapshot, use the More on the selected date to choose which to view.
5. Tick the Compare historic version to current check box.
Differences between the current version of the project and the snapshow will be shown per column as well as in the timeline.