Yes, that is true, most of the big companies have some kind of cut-off for 10th and 12th and that varies from company to company. Nevertheless, there are lot of other companies, who do not impose any such cut-off for 10th and 12th marks. So, I believe you shouldn't simply write off campus interviews. You should still try and if you are good, you may get hired from campus selection.

As for your other question, you may consider doing MBA or M.Tech, depending upon your aptitude and ability to cope up with extra pressure and effort which is required to prepare for any of these entrance examinations. Lot of students join MBA and M.Tech immediately after B.Tech. So, you'll have to judge yourself, based on your own capability whether you would be able to take the extra load and how much would it affect your B.Tech.

Hope this helps.

Counselor CareerAge.com