At
https://gmatclub.com/forum/breakdown-of- ... 33151.html
you can download a spreadsheet which shows which questions in OG 12 correspond to which questions in OG 13. That, in and of itself, doesn't tell you which explanations are the same and which are different, but at least it's a complete list of which SC questions have been repeated and where.
I don't know, but if I were a betting man, I would place a large sum of money on a bet that GMAC did not alter one syllable of explanation for the SC between OG 12 and OG13. They are all about recycling everything they can.
I hope that helps. Let me know if you have any further questions.
Mike
