If you do something regretable in Beyond Compare, how can you get your old files back?
In TextCompare, there is undo: Ctl-Z
In FolderSync there is NOT an undo. You have to enable "BackupFilesBeforeCopy" or "BackupFilesBeforeSave". These settings are in Tools->Options->Backups
When those are turned on you will start to see lots of files accumulate that have a .bak suffix. (You can set this suffix to other options at Tools->Options->Backups.) Here is a folder with a file and its backup file: