Within the Testcase Creation application, each testcase has a "History" button that shows previous versions of that testcase and who modified it on which date. This allows you to:
View the details of the previous versions of the testcase
Compare any two versions
Rollback to a previous version of the testcase
Clicking on the "History" button shows the following list:

The latest version is shown on top with all previous versions shown subsequently with details about which user saved it last and when. Any version can be selected and clicking on the "View" button shows the details of that particular version:

Any two versions, in any order, can be compared by selecting the appropriate radio buttons in the list and clicking on the "Compare" button. On doing so, the version being compared to shows up second in the list with all the "diffs" or differences being highlighted appropriately.

After a determination is made about which testcase version to rollback to, selecting the radio button at the bottom left of the screen and clicking on the "Make Current" button will immediately replace the latest version with the version you have selected to rollback to. In this example, Ver 1.4 was determined to be the version to rollback to; so on selecting it and clicking on "Make Current", its rolled back to that version (by creating a new version, Ver 1.6).
