Hello aspirant

Yes you can again study class xii or you may go for class improvement exam for chemistry.

There are many universities that offer class improvement exams for failed students or droppers .

NIOS is one of those universities where you can study and appear for chemistry exam.

NIOS is National Institute of Open Schooling.

NIOS is government recognized abd nios marks are accepted every where in India.

So you must join nios and reappear for exam , pass out it and then you will be eligible for neet and further studies.

Good luck.