Cadre wise benefits/ salary and subject selection
 

Hi
I am preparing for the exam-2021. I have opted the subjects IR, Indo-Pak history, Environmental science, Muslim Law & jurisprudence, and sociology. I have an engineering (Chemical) background. Any suggestions to replace any subject? Any preferable subject for a specific cadre?

Another question I have in my mind is about the benefits/salary of a css officer. I came to know that after passing through all the lengthy selection process successfully, a 2-year training program will be awaiting your way. After that you will have to go through a 1-2 year internship like program for practical experience in the field. Only then you'll be able to have annual increments and promotions. What is the total salary/benefits at early stages? If the salary is around 30-40k and nothing else for so many years, why there is so much craz about it? How do you compare the difficulty level of the hiring process with that of the other same scale jobs, when it comes to the salary?
Thank you for your valuable response.