Hey n2739178
1. I don't know if that's the case, but the OG12 has been known to be quite representative of the actual GMAT, so depending on what GMAT decides to be your score range, you may or may not receive such hard questions.
2. I think it's a good strategy as long as it doesn't get to a point where you're getting the answers right by memory rather than logic. Looking up the concepts you got wrong initially and finding out why you got them wrong is a definitely good strategy to follow! And maybe you can consider using an
error log. There are many that have been posted on this forum. Just search for it
3. I've only looked through the Number Properties book but I think that it's a pretty good guide as far as GMAT goes, since most people who prepared for Quant through
MGMAT are generally satisfied with the outcome.
Hope this helps!