Law

To become a judge, first of all, you will have to be a graduate in law.
The students from any stream can take up the law course. So you can choose Arts also in 11th
After completing your 10+2 studies you will have to give some entrance exams for doing the L.LB One of the most common entrance Being CLAT (Common Law Admission Test )
For appearing in the CLAT exam you must have completed 10+2 studies with a minimum of 50% marks. However a relaxation of 5% is given to the SC/ST/OBC and physically handicapped candidates.
The criteria for Most of the other entrances will also be the same. There may also be an upper age limit of 20 years for General candidate.
But these may vary from one entrance exam to another.
In CLAT exam questions will be asked from Legal aptitude, logical reasoning, English General Knowledge and elementary mathematics.
After completing graduation in Law you will have to give the Judicial service exams. These are state level exams conducted by the respective state government.
To be eligible for this exam you must have passed all the exams of L.LB in first attempt and also you must have secured a minimum of 55% marks in the final year examination.

CS and LLB is a great combination as both pertains to the compliances. A person having dual degrees compared to only CS degree will be preferred more by Companies.
However, as regards comparison between CS and CWA, the choice will be yours. I can only guide you about the CS course. It is basically more of a theoretical course as compared to CWA. Even in the practical papers like FM, Cost Accounting etc you will find that the general pattern of questions is more of a theoretical nature. I have seen student cribbing about the presence of theory. So if you are not accustomed to learn and write long answers, please do not enter the course.
CS course has 3 stages: Foundation Program, Executive Program and Professional Program. If you are lucky enough to clear all the stages in one go and including the training period of (1.5 Years), the duration of the course comes to 4.5 years.
ICWA has training period of 3 years and the course is of practical nature as compared to CS. You will become a master of Cost Accounting (CWA) as compared to CS wherein you will be an expert of Company Law and compliances.
In short, both the courses have their own methods and techniques and you will be the best one to decide which one to go for. As far as concerned with opportunities, there are ample in both of them.

Yes, you can take admission in 3 years LLB course without having to appear for entrance exam. There are colleges who offer admission on the merit basis.
LLB is a 3 years long course which has started to be replaced by BA LLB course which is 5 years long. Most colleges these days are preferring to offer BA LLB course to the candidates which can be taken after completing 12th standard. It is mandatory to appear for entrance exam for BA LLB course. The name of entrance exam is CLAT.
There is however no such requirement for LLB course. You can seek direct admission based on the merit. You will have to appear for an interview after which you will be given admission for LLB course.
Although not every college follow this procedure and a large number of them prefer to select candidates through entrance exam. The criteria for entrance exam is:
Eligibility
1. A Bachelor degree in any stream.
2. Minimum of 45 percent marks in Bachelor degree.
3. SC/ST need 40 percent marks.
4. Age limit for LLB is 30 years.
5. SC/ST gets 5 years relaxation in upper age limit.
The criteria for admission based on merit is also same. However you will need to have good percentage to make the cut. Below are some colleges that offer admission through merit.
1. Government Law College (Mumbai)
2. Balaji Law College (Pune)
3. ILS Law College (Pune)