Hello,,

To be very honest the answer of your question is NO ,you can not get cs by only attempting the class 12 th question in jee exams because there is very tough competition for CS branch in good colleges and if you will attempt only class 12 questions and left class 11 questions you can not stand on that competition. If you have prepared your class 12 syllabus,I will recommend you to cover class 11 ,not full syllabus but some selected and scoring chapters and there are many chapters in physics chemistry and maths which will enhance your marks and you can score a good percentile and secure good marks ..

The ratio of class 12 and class 11 syllabus is of 60:40 so class 11 is also important to secure a very good rank...

Let us Suppose if there is total 10 questions in which 6 is from class 12 and 4 is from class 11 and if you attempting only class 12 you will left 4 questions and you are out of competition in prospective of your branch but it is very easy to cover class 11 ,if you prepared the class 12 in very well manner,you should prepared for class 11.

Hope you understand well!!!!