Hello buddy!
Board exams are very important in any student's life as these are going to help you get a good college. In top universities such as Jawahar lal Nehru University (JNU), Delhi University (DU), admissions are given on the basis of your 12th class marks. Not only this, you can even get scholarships if you have the desired marks in intermediate. The pattern of board exam is similar every year. So, one can even predict the questions. Like in English novel section, the description of characters repeat and therefore once can predict it.
Step marking system is implemented in Board Examination which is student friendly. If you get a wrong answer but if you have followed correct procedure, then you will be getting marks for this. So if you have attempted all questions and you know concepts of all, then you will get nearly 40 marks. The step marking system will fetch you marks for the steps, not the answer.
It is commonly believed that since the examiners have a lot of copies to check, so they don't go deep into the answer.  If we think practically, this seems to be true. The way you present your answer also matters. Use paragraphs properly, and try to answer in points. This will be easy for examiner to check.
Here's the links of Board exam sample question papers :
Physics: https://mycbseguide.com/downloads/cbse-class-12-physics/1251/cbse-sample-papers/2/
Chemistry: https://mycbseguide.com/downloads/cbse-class-12-chemistry/1267/cbse-sample-papers/2/
Math: https://mycbseguide.com/downloads/cbse-class-12-mathematics/1284/cbse-sample-papers/2/
Biology: https://mycbseguide.com/downloads/cbse-class-12-biology/1298/cbse-sample-papers/2/
English: https://mycbseguide.com/downloads/cbse-class-12-english-core/1855/cbse-sample-papers/2/
Hope you are satisfied.
Thank You!