There is no way to delete a "Saved" version of an application. The "Delete" button is enabled for Live version (or prior) but not for "Saved" versions ahead of that.
The goal would be to basically revert to the last Live version of the application. Please enable a feature that provides the mentioned ability to manage app version.
You can now restore older versions of your app - https://docs.microsoft.com/powerapps/maker/canvas-apps/restore-an-app
Thank you for your feedback. This appears possible today, just not for the current version. If you create another version, simply create another change you can then delete the previous version. So...
1. Save a new version with the desired changes then you'll be able to delete that one.
2. In the case where you want to restore to a previous version (this would move the restore above the one you want to delete), after restore to that earlier version you can delete the version you are pointing to.
can i revert all power app form version and restore to list default versions ?
In the current state you can not get rid of any changes you have done to your app since the last live version. It is impossible to revert to the "live" state without first publishing the latest version (which in my case is broken). Do I seriously need to publish that broken crap, before I can revert to the current live version?
This is not complete. AL89 is correct. There is no way to delete a saved unpublished version to revert back to the most recent published version.