See, you cant get a B.Tech degree if you have backlogs so you cant any way apply unless you clear those backlogs. They generally check the overall CGPA but yes they may even look at all semesters. However, if you have a plausible reason and then clear those backlogs in time, there should be no reason why you cant pursue MS. As far as count is concerned, it depends from university to university and course to course so one cant simply generalize. I suggest that you concentrate and clear those backlogs if any and then apply. No reason why you cant if you have completed B.Tech and wish to pursue further studies.