First of all i would like to tell you that you cannot do 28 papers in just a week !! You can do maximum of 7 papers. Now, whether you can score 500+ or not it depends a lot on your previous preparation. But if you are determined to score 500+ then you will definitely score it by doing previous year papers (specially after 2010). The only thing you have to do is to revise at least 2-2.5 hr after every paper after doing it (you have to revise incorrect as well as correct ques). Then you will be able to correctly identify that where are you lacking.
Also please note that MTG has many mistakes , so please cross check the answers which you identify as suspicious.