No. It is not possible for a 12th passed student to apply for the IAS exam, as the exam requires a minimum educational qualification of being a graduate with a bachelor’s degree from a government-recognized university.
So, if you are a 12th passed student, I’d recommend that you get yourself a college/university degree first, and then apply for the UPSC IAS recruitment.
Iet us now take a look at the process of the UPSC apply online.