should we attempt all the questions,is it compulsory to write all the questions
No it is not mandatory to attempt all tge questions in KEAM. The exam consists of two papers-
Paper 1(Physics,Chemistry)- 120 questions
Paper 2(Maths)- 120 questions
4 marks will be awarded for correct answer and 1 mark will be deducted for wrong answers. So, since there is negative marking you have to be more accurate while attempting the questions.
For detailed info regarding exam pattern-
https://www.google.com/amp/s/engineering.careers360.com/articles/keam-exam-pattern/amp