Several characters have visited the Oracle of Apollo at Delphi in an effort to obtain guidance. Do you believe that advice given to each was harmful or helpful?

I am not sure what the ACE format is, but the answer to the question you are asking is more an essay than a short answer which is the way this site should work.  However, in the case of this play, Oedipus is told what will happen and he tries to avoid his fate by doing something he might not normally have done.  That, in some sense, is harmful because when he leaves Corinth and goes to Thebes, he actually fulfills part of the prophecy that he would kill his father.  The advice certainly forces the characters to make choices to find a way around the prophecy which ultimately makes the character walk right into his destiny.