Can I join merchant navy after completing B.Tech in IT? What are the opportunities after completing the same?

You can join, but your academic qualification will be completely different from your job role, then you may get opportunities into core sectors like aviation, defence, metallurgy and lesser opportunities into IT stream.

Yes, you can join it after completing B.Tech. You can check the below mentioned link: https://www.jahajee.com/join-merchant-navy/BE-B-Tech_INDIA/?c=lt28