Hi Ashish,

As you must be knowing the All India Bar Examination is conducted to assess an advocate’s capability to actually practice law in the country. And yes, it has been made compulasary for all law students graduating 2015-2016 onwards. It is only when you qualify this exam that you are given a license to practise law in India, without which if you practise your study, it will be termed illegal and you can face severe consequences for the same.

Therefore, no, you cannot use the vakalatnama before giving the exam or even in the case of failing the exam. 

I hope this was helpful, all the best!