I failed in 1 subject in class 12th Bihar Board and missed the compartment exam. Should I appear next year for this one exam only?

No, you have to sit for every subjects next year. Because if you failed the annual exam and missed the compartment exam as well, then that means you failed in that course for that year. But you can reappear for the course again and give the exam very next year and complete your course. Check the not

If you have failed one subject in the Bihar Board Class 12th and you missed the compartment exam, then you can appear for the exam the following year. You have to repeat the whole year and rejoin the course for which you failed. You must pass with at least 30% marks in theory and 40% marks in practi