how can everybody score in 700's in MGMATCATs
Everybody?! No, you probably took other people scores from GMAT Prep. Scores above 700 on MGMAT are rare, I've never scored that much and yet took 720 on the real deal.
Before start freaking out and asking yourself were you stupid (and you are certainly not), you have to take GMAT Prep. That is the only way to know your current performance - MGMAT scores mean nothing. The fact that you haven't answered on last 10 or so questions on MGMAT also means nothing. That is perfectly normal, their questions are so insanely difficult and long that average 700+ test taker struggles to even read them under two minutes, not to mention to answer them.
Just don't worry and do GMAT Prep. And yes, don't forget to post your results here.
My GMAT experience
My retake experience - GMAT dropped from 720 to 690 - advice for retakers
My TOEFL experience - 108
Find out what's new at GMAT Club - latest features and updates