As per my suggestion student should start writing sections and case laws at the PCC level itself. I would suggest you to make it a habit to remember sections along with case laws as it will surely help you a lot during preparation for CA final or other professional examinations. Section and case law knowledge is also very important for your professional working. It is 100% true.
Keep one thing in mind -- write the sections and case laws only when you are 100 % sure, otherwise leave it.
However let me tell you one thing you can easily clear your CA without sections but for me it is all about standards. Now the choice is yours.