If you are not happy with the changes you or someone else have made to the subtitles, you can easily switch to any earlier subtitle version of your choice by clicking Roll back to this version button at the bottom of the page with the desired version:

When you click this button, Amara will create a new subtitle version after the last one, which will be identical to the one you've selected. 

Please note that the versions that were created after the one you selected to roll back to, will not be destroyed - they will remain visible in the revision history. If you really need to completely hide a particular version from view, please ask Amara staff to do so, stating why this is needed.