Government & Defence Entrance Exam

You don't have to apply to RAW. RAW sends out invitation to best officers in department. RAW recruiters personnel from IPS, IAS IFS, Army, etc. So you don't get to choose if you have what it takes to be a RAW agent, you will automatically be noticed and get invite for recruitment.

If you have done 12th and pursuing graduation then prepare for SSC CHSL for 12th level along with SSC CGL for graduation. Other than these, railway releases vacancies each year for both 12th and graduates. Also, each state releases its own vacancies several times a year. So it means there are several options available. Read newspaper to know about the vacancies.

It would be fine if you can manage both studies at once. Your B.Sc should help you in your IAS preparations as well. Add details about your locality and course you pursuing to get better answers. But usually most people begin their preparations in the 1st year itself.

Public Sector Undertaking (PSU), most of them recruit graduate engineers as trainees / probationary engineers every year. There is no common entrance test for that as the requirements are company specific.
Candidates who are in the final year of graduation can also apply for PSU Jobs. The eligibility criteria of PSU jobs vary from company to company.

SSC CGL syllabus is composed of Reasoning, General Science and English. To prepare for SSC CGL it is best to join a coaching to learn systematically. And solve a lot of question papers.

ISRO releases vacancies for Junior Assistant or Researcher once in a year. Only Masters graduates are eligible. Different vacancies are released for different subjects.

If and only when they are in same city and their timings don't conflict with each other. NDA exam is usually conducted in morning at around 10.

It is tough for even bright students who score 90+% but it is not impossible. It requires a lot of hardwork that means 8 hours daily. The selection ratio is quite high for UPSC exams. So, one needs to be completely dedicated towards the studies.

Joining a coaching is the best way to prepare. You will be easily able to understand complex topics in a coaching rather than studying yourself.

What is your qualification and age? Without these details a proper answer can not be given. But still here are some options.
1. Through direct entry after 12th (Merit based)
2. Through NDA
3. Through CDSE ( Technical Graduate)
4. UES (Technical Graduate)
5. TES
6. Airman and Ground Support Staff.