Hi Wendee73,
As far as a source of retired, Official GMAT questions is concerned, the OG13 is fine - so you can use that book without any concerns (and you don't actually need the GMAT2020 or GMAT2021 to prepare for the GMAT). That having been said, none of those books were designed to teach you Tactics, patterns or the little 'secrets' behind the GMAT - for those, you'll need Course-oriented materials. To that end, you might want to work on the OG (whichever version you use) a little later on in your studies. As far as the other books you have, you might want to reach out to
MGMAT directly to ask about the differences between those older books and the most recent set of books available. Academically-speaking, the content of the GMAT has changed very little over the last 5 years, so you'd probably be fine with those books as well.
From what you describe, your immediate study plan is 'book heavy'; unfortunately, many Test Takers who study in that way end up getting 'stuck' at a particular score level. There's no harm in starting off your studies in that fashion, but you'll likely end up needing to invest in some additional, non-book resources at some point. Before I can offer you any additional advice for your studies, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) How long have you studied? How many hours do you typically study each week?
2) Have you taken any practice CATs/mocks yet - and if you have, then how did you score on EACH (including the Quant and Verbal Scaled Scores for EACH)?
Goals:
3) What is your overall goal score?
4) When are you planning to take the GMAT?
5) When are you planning to apply to Business School and what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich