Please help guys regarding BSEB board

I am currently in 12th grade and paper is starting from 1st of Feb .Paper is of Biology can I repeat class 12th and change my stream from PCB to PCM ...I really want to do it ..No matter what. Can I do 12th again after passing it once from PCB Or do I have to fail in PCB ..Ready to do that (Glti se pcb select kr liya hai pcm Krna tha ab baaki chize mt puchna bhai ) 11th maine PCM se hi ki thi