Can I give IAS exam or not? I got supplementary in 12th.

You can only give IAS exam, once you have done your graduation. For that, you have to qualify your class 12th exam too. So, first you have to clear your supplementary exam, then only you can go for IAS after your graduation. All the best.

I never searched for this. But I guess if you will clear your supplementary then you will be able to give the test for IAS. You will be more clear if you search it on the internet i.e. eligibility criteria for IAS exam.

Minimum qualification required to apply for IAS is you should be a graduate or completed your graduation. Marks doesn't matter. All you need is to pass. Yes you can apply for exam. All the best.