I've got 75% in 10th 87% in 12th & 75% in degree (B.sc) probably if i can expect a call from iim Lucknow 90%ile in cat
See, your academics are the most problematic things, as with 75%, 87% in schooling (10th and 12th), and 75% in your graduation, you are in quite disadvantageous position. And since you are in B.Sc, you'll be counted in the same bucket as engineers, you you'll get no diversity points as well.
The best thing will be that you re-attempt CAT after getting some work experience, because workex is the only thing which can counter all the negative things in your CV. All the best!