Computers & IT (Non-Engg)

You may do the course from the below link:
https://www.edx.org/course/introduction-game-design-mitx-11-126x-0
You may also refer to websites like coursera and udemy for the same.

Jetking Infotrain Ltd is a good institute to get into the same.

There are some norms of territorial jurisdiction. You will have to check with the college you wish to get into.

There are no disadvantages to do this course. You may refer to the advantages in the link below:
http://ignite.tcs.com/igniteAdvantage.jsp#.V9ZBCZh97IU

Students who have completed/completing degree B.Sc / B.Sc(Hons)/ BCA/ BIT of 3 years from open universities are eligible to apply for NIMCET provided their programme is approved by UGC /AICTE and Distance Education Council (DEC) of Govt. of India. You may check whether your BCA degree meets the eligibility criteria.

Comparing both the courses would not be the right thing to do.
After BMM, you can become an anchor, a director, a journalist, a photographer and can go into similar professions. Whereas, after B.Sc in IT, you can become an IT engineer, associate engineer, systems manager/engineer, database manager, database security professional, software developer or software tester.

These are two different fields, dealing with both at the same time can prove to be difficult. If you want to get in the teaching line then opt for B.Ed along with a subject similar to MCA.