Well as far as which essay to address it in, I think you could make a case to address it in that essay prompt (which not all schools have) or the optional essay. Since your undergraduate studies were a little haphazard, your GMAT, recommendations, and work experence, and essays will get more scrutiny.
So remember, however you choose to address it just show how well you were able to overcome it. Maybe your business could be that adversity and you could discuss how it changed and molded your different undergrad experience, and what you learned and how you overcame this adversity. Although I'm not a professional in the field, I do believe you have a shot, and just remember that you can sell youself in this essay WHILE mitigating the negative aspects of your undergrand.
So push forward, and put together the BEST application you can. Your past is the past, and can't be changed, so the more time an effort you put towards your future, the better of you'll be!
Good luck, and definitely come back and let us know how it goes!
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