Law

The eligibility to become a Judge is Graduation in Law Degree or LL.B.
The LL.B. can be pursed in two ways :- After 12th 5 years Integrated Law Degree and after Graduation 3 years Law Degree.
You can apply for 5 Years Integrated LL.B. course after 12th from any stream with 50% marks from a recognised Board within the age of 20 years through entrance exam like CLAT(Common Law Admission Test).
On the basis of the score in CLAT you can be admitted to top Law schools under NLU(National Law University) and other Universities.
After Graduation in any stream you can apply for 3 years LL.B. course.
To become Judge in India there are two processes. First is to become a Civil Judge grade-II through qualifying exam, conducted by respective high courts. They invite applications based on their vacancies and conduct exams in multiple centers. The Judges so selected are given Magistrate posts who upon seniority, rise to become civil judge, judicial judge and senior judges. Second process is by selection of senior advocates by the Collegium of Judges. In this process, senior advocates with good reputation are selected without any exams.
After becoming Judge, a person rises from lower courts to high courts and Supreme court based on seniority, reputation and other parameters like cases solved per month/year etc.

Dear Bhavuk,
As a commerce student, you can definitely pursue Law. Though you have not specified your previous qualification, assuming it to be 12th, you can go for Integrated BBA LLB, Integrated B.Com LLB course.
Opting for these Integrated courses will save your one year. You will be able to finish off your degree in 5 years, thus saving one precious year of your life as well as fees for one year. Otherwise you have to spend 6 years, 3 years for BBA/ B.Com and 3 years for LLB.
Some of the good places offering Integrated Law courses are NALSAR, Lovely University, Bennett University, etc. All these places offer admission on different criteria like CLAT, LSAT, their own tests, marks in 12th, etc.
Check their websites for more details.
Good luck.