No you can't. If you want then you will need to repeat class 11 in arts stream. Because these both streams are totally different.

Yes u can for ur final exams there will be separate login option then u can go through it and u can pay exam fees any way once you go to haryana board of intermediate education

Hey Shailja.

I understand that you do not want to continue science stream for your class 12 board exams. That would have been perfectly okay if your school had not enrolled you for your final class 12 board exams. If there is a possibility that you have still not been enrolled for class 12 board exams, you have a chance to get your subjects changed by requesting the school authorities. But if by any chance you already have been enrolled, then I am sorry to say but you cannot get your stream changed.

Hope this serves your query. Please feel free to respond and ask further questions.
All the best.