Hello student ,

First of all I will suggest you that you should go through the eligibility criteria to become a sub inspector as only written exams will not help you to become sub inspector you have to check your physical character like height , weight and chest . So after completing your final year b.tech you can apply for it as it is better option if you want to go for govt job in this sector it will give you even more benefit and for joining this defence post, engineering  bachelor graduates will have to appear for CDS Exam conducted by UPSC every year.

Hope you find it helpful for further queries you can ask freely in the comment box.

Good luck !