Leslie Judge

I was thinking about the Vader killing Anakin issue.

If I'm correct then in the OT nobody evers says that a Jedi can't teach more than one padawan, so Obiwan could have had a group of students. He even says '...who was a pupil of mine...'

If Vader's name comes up earlier so we know that a Darth Vader exists somewhere and he is a former Jedi who turned to the dark side, then Anakin could be sent after him alone or with a few other Jedi to capture/defeat Vader.

If we see Anakin go on a mission at some point in the movie and later Vader comes back telling Obiwan that Anakin is no more then only Obiwan knows what he really means and who he really is (if he can sense his true identity), we don't.

During their conversation/fight Vader could refer Obiwan as his former master, so Obi wouldn't sound such a liar in EP IV.

Of course this means that Anakin should have turned to the dark side earlier and that he is good enough with the Force to hide this little fact from the other Jedi.