The full list of all the subtitle versions is displayed on Revisions tab on the subtitle page:
You can see who and when created each version and how it was created (through Subtitle Editor, Legacy Subtitle Editor, Upload, or API, or rolled back to a previous version). You can click any revision (subtitle version) to view it, or check any two revisions to compare them.
By default, only the 10 most recent revisions are displayed. To view more, please click Show More button at the bottom: