Civil Servant (IAS/PCS)

The whole power of district rests in the hands of district collector.

Civil services exams are really tough. To crack these exams, you have to understand the pattern and type of questions asked every year.
Also, as you have done BE, your reasoning and quantitative aptitude techniques are required to be polished.
For this you might need to join some coaching or online test preparation course.
For GK, you need to focus on current affair and newspaper reading.

The qualification for IPS is you must have attained 21 years of age and you must have your graduation
degree from any recognized institute. You can choose any stream in your graduation.

Search for the best institute. See its faculty background and experience. All the institutes can show you a
path for civil preparation. But, it is you who has to do hard work to achieve your goals.

Read each and every NCERT subject book from class 6th -12th. Also, focus especially on your Bachelors' major subject.

2.5 lakh per month will be the salary for highest post in IAS.

Every subject has its own importance. UPSC will test your knowledge on all topics. So, I can't say that law is beneficial or history is beneficial.

Yes, because you will have only limited attempts to appear for the exam and if you don't fare well in UPSC then you have various other options like SSC-CGL, PSC, bank exams which are far easy when compared to UPSC.

You must have attained 21 years of age and you must have a graduate degree from recognized institute. You will be given IAS or IPS according to your rank.