Is eligibility criteria of good scores for 12th very important in getting a job in an MNC?

Generally, Many MNCs will see for at least three first classes out of four stages of your education that is 10th, 12th, graduation and PG. Some MNCs will see for 2 first classes in the four. Some companies only look for your PG score. That depends on the individual policy of the company. As far as my experience goes, once you attain the minimum qualifying criteria, then they will go for selection based on your performance in their screening procedure. But you need not worry much about that. Minimum chances are there for you to get rejected because of not getting first class in your 12th,

MNC follow certain criterias in the process of recruitment however, it would all vary from company to company. There are some companies who would insist on scoring on high first class marks at each stages from class ten to the last degree one has passed.
However, there are certain organisations ignoring such criterias. They would clear your screening even if you have failed to achieve the minimum scoring in one of the examinations.
In your case, other than your performance in class twelve Examination, marks are acceptable for acceptance - purposes.
So, you need not worry on that account and devote to your studies so as to get an impressive scoring in the remaining semesters of MCA examination.

Generally MNCs will see your performance from class 10 to MCA but MCA scores will be given a preference. For example if you have very good scores in 10, 12 and BCA but poor in MCA then there may be a problem in your selection. Once the eligibility for a post or job is MCA then naturally the scores in MCA take a precedence.

Anyway if you complete your MCA with high scores you fare a good chance in the selection irrespective of your lesser scores in earlier classes.

Some companies give marks to earlier class scores and add everything with the last one that is MCA in your case. In that case all the scores become important. So it exactly depends on the methodology they are following for the selection process.

There is a saying, "A Single Sheet of Paper cannot Determine My Future", and we all casually use it as an excuse for low marks. Well, in fact the statement is true.

And I believe that MNCs are smart enough to understand the meaning. Let me explain. There are people who gets great marks and finds it difficult to work under the given conditions, and there are people with average or lesser marks who does well in work and almost all companies know this. So, don't be afraid due to low marks.

Then what does really matters? Well there is a host of things that came to be taken care of. This includes communication skills, presenation skill, stress management, and lot more. And the employers put weight on these more than marks to an extend. Who knows, marks can be obtained by cheating but not these stuffs can be.

Does that mean marks mean nothing? Absolutely not, marks are needed, and it can help us to get chances easily. Consider the situation for instance. You can contact someone via a feature phone. But then there are smartphones which also serves the purpose, but in a better manner, say Internet, voice mails, etc. So, marks helps you in having a good first impression, and then it's all in your personal skills anyway.

Before winding up, just one more thing. Your marks have a huge difference in tenth and plus two, which will be almost a sure concern. Be prepared with the reason of that bug difference, hope you got something genuine.

All The Best!!