Agreed that you shouldn't use the "1000" source questions. We've banned them from our site - we won't even discuss them. :)
Even at a level of 50, you will not get all of the questions right - that's not how the test works. You should expect to miss multiple questions - many more than you would be typically used to missing to get such a high score on a regular test.
If I solve MGmat Advanced Quant book thoroughly, will I cover almost all 700-800 level problems easily in Main GMAT exam?
First, I can't say that just because somebody does that book, s/he will then get everything right on the test. I can't predict the future and I don't know how well you'll actually learn what the book is trying to teach you.
The Advanced Quant book will certainly help you to learn how to do hard problems - but note that this book isn't a "math" book. It's a "how to think / solve" book. You're really learning how to think flexibly and find better / faster / more effective paths to even those questions that you haven't seen before.
The AQ book assumes that you have already mastered the material in the 5 regular books. If your overall quant score is about 75th percentile or higher, then you'd likely benefit from AQ. If your quant score isn't at that level yet, then you may have some more work to do before AQ is a good tool for you.
You list enough practice sources that I'm worried you might have a bigger problem: I'm worried that you're spending too much time doing and not enough time actually learning. When you're *doing* a practice problem (or test), you're NOT actually learning (not much, anyway). You're simply trying to use everything you learned before you started working on that problem.
Read the "how to learn / study" section of this article in order to learn how to learn:
http://www.manhattangmat.com/blog/index ... -the-gmat/Finally, if you want to avoid spoiling yourself on GMATPrep questions, do NOT do the 1000 sets - there are some GMATPrep questions (unlabeled) floating around in those sets.
None of our materials contain GMATprep questions, nor do the most recent OG books (OG13 and the 2nd edition quant and verbal supplements). If you use our forums, avoid the two folders labeled GMATPrep.
(Other test prep companies also won't be using GMATPrep questions right in their books / materials - nobody can, because the copyright is owned by GMAC.)