Anakin's ghost in ROTJ is not possible

I was just watching ROTJ and realized that there was no way Anakin could have appeared as a ghost at the end of the movie.

Anakin never learned how to achieve eternal concience as Obi-Wan and Yoda had, so what's the deal with that?

Also, why was he wearing Jedi robes which he never in his life wore, what happened to his darker leather ones?


TLJ Edit: There must be a dozen links to Hayden-Ghost-Threads all of ther place. Find one. Any one. I'd start in the index.