Hello Krishang Saxena,
I think that you should go for supplementary exams and then go in 12th. Try to cover the previous class concepts which are required in 12th and if you want to appear for any entrance examination then  you should drop a year.

Dear krishang,
You don't need to take stress or tension about the supplementary exam. You have to start preparing for your exam with your faith and confidence.
Because the time is so precious for everyone. Don't ruin your hole year to repeat the same class .As you told me that you have one month left for exams so, make a time table and distribute between both the subjects and try to pick the topic which are easy for understanding.
Most important thing is that supplementary exams are quite easy as compared to normal exam .
Never give up in your life.
I feel glad to help you .Best wishes for you exams