If a survey has been deleted from your account then all results of the survey report are also deleted and are not recoverable.
Similarly, if a question or answer is edited and saved, it is not possible to restore a previous version, although the question/answer could be edited manually again.
When it comes to editing or deleting surveys we recommend simply disabling outdated surveys and creating new ones. This can be done from Settings > Candidate Surveys by flipping the on/off switch next to a survey.
Also, note that when a candidate is deleted by a user, candidate, or system action the survey responses will also be deleted and are not recoverable.