BCA

BCA undoubtedly is a better course, as DCA is only a diploma course and BCA is a full time UG course. Even the job opportunities and scope is far better for the BCA course.

You should pursue B.Sc in electronics.

These two are totally different courses, you can't compare them.
You should choose that one whichever suit your needs.
If you are interested in computer programming language and want to make career in this field then you must do BCA, otherwise B.Sc is also not bad.
The choice is yours.

St. George College of Management Science and Nursing, Bangalore is the best college.
Check out the official link below for admission details:
http://www.stgeorgecollege.org/academic/bca.php

NIOS board is also valid for admission to maximum BCA colleges across Mumbai:
Check out the link below for details:
https://it.shiksha.com/bca-colleges-in-mumbai-all-categorypage-10-100-46-0-0-10224-1-2-0-none-1-0#cateSearchBlock

Yes, MGKVP do offer BCA course.

You can do B.Tech or BE after BCA if you had PCM subjects in 10+2 stage. BCA grads are not eligible for lateral entry admission in B.Tech. Only B.Sc or three years engineering Diploma holders are eligible to seek lateral admission in second year of engineering degree courses.

Both the fields are same, but B.Tech in IT will provide you better career options. So, you can opt for B.Tech in IT.

BCA provides basic skills on programming. If you have ideas and creative mind, you can design games after completing BCA. However, in order to become a designer in gaming company, you may have to gain sufficient experience and expertise.