hey ravi,
coming straight to u'r second question, no one can actually answer it

.
having excellent marks in acads does not mean that u wud be thru, and at the same time having bad marks does not mean that u wud not be thru.
u can take my example as the best one
i got a call from NITIE, which is supposed to be an institute that lays more stress on academic marks in the selection process. i stand in the top 3 of JNT university
in electrical engg, but got kicked off on my a** in NITIE

as i cudn't substantiate my marks. i cudn't answer basics of electrical engg

.
so, if u have really gud marks, the problem will be a bit more complicated , as u have to substantiate them.
not having good marks doesnot imply rejection, as i can show u umpteen number of ppl in the premier mgt institutes with academic %ages than 70.
so i hope that u'r doubts r clarified.
any ways,
ALL THE BEST
vijay