Courses
1) C language
2) Java
3)C ++
4)python
5)Oracle
Competitive exams :
Please be precise about it.If you want to remain in India,then go for DRDO,BSNL etc.or any other Psu which takes computer graduates through a specialized entrance exam
Writing GATE can be a good option as many government organizations have started using GATE scores heavily to recruit candidates for them
Good luck!!

Hello aspirant
As a computer science engineer you must give the following examinations for your career:
GRE- graduate record examination.
CAT- common admission test
GATE
UPSC
CDSE
Civil cervices examination
Decide whether you want to join the civil services or do an MBA or continue with MTech and then write the exams accordingly.
Hope this helps.

As you are doing cse then go for competitive coding like codechef, codevita, codeforce, codebits. It will increase your coding efficiency. It will help you in interviews and placements. You can also study for gate from second year. If you are a MBA aspirant then polish your English and reasoning skills 

You can give civil exams during your btech, you can give nda once again or wait till your graduation complete. You can even give JEE exam again if you are preparing in between. All the best!