Hey,
Bachelor of science in Nursing is a four year long undergraduate programme. The minimum eligibility criteria is to pass 12th from any recognised board with Physics,Chemistry and Biology.
The cut off depends on the institution in which you want to take admission.The cutoff is decided on many factors and some of them are mentioned here.
Number of candidates appeared for the B.Sc Nursing Exam,number of candidates who passed the exam,Difficulty level of question paper,Number of vacancy for this post,Cutoff may also be sectional wise. The cutoff is subjected to variation every year.
Hope this helps.
Good luck.