Hey there buddy, some colleges accept with the 12th score and some consider entrance exam,There is no specific cut off mark as it varies with exam and competition and the quality of the paper,etc.The entrance examinations have negative marking of 0 to 1 mark.The number of questions ranges from 150 to 200. The time allotted for the exam is 3 hours.The syllabus for the entrance exam includes questions from

Physics

Chemistry

Mathematics

Biology

Hope this helps, Good luck