Certification

Hello Ajinkya,
You can go for certification courses offered by Oracle:
DBMS
Core Java
Advanced Java
If you're interested in networking you can pursue CCNA (Cisco Certified Network Associate). It has a great value and is valid for I guess two years. So, you may want to apply for it in your final year of engineering only.

Hello Dev,
IATA is a course for to understand fares pricing of international and domestic airlines.
It has a scope in airline and tourism industry you get thru with the world geography airport codes and areas.
IATA means International air transport association which is associated with all airlines.
IATA certification is from Canada Montreal they have introduced various courses related to airline and airport operations apart from the original fares ticketing pricing you can visit IATA aviation training and you will get lot of information on the courses offered. Once you complete IATA you can opt for jobs in travel and tourism industry.

No, its not necessary, you can prioritise on the basis of your interest and scope of each certification.

You should pursue an MBA through distance learning from any of the top 20 MBA schools.

I would certainly name UEM, Kolkata best suited to your need and has good consistent placement record. Visit https://www.shiksha.com/university/university-of-engineering-and-management-kolkata-47398 to know deep about its courses too.