Course comparison

Here, the difference is based on the curriculum.
Computer Science students study Algorithms and Data Structure, Architecture, Artificial Intelligence and Robotics, Database and Information Retrieval, Human-Computer Communication, Numerical and Symbolic Computation, Operating Systems, Programming Languages and Software Methodology and Engineering.
Information Technology deals with installation, development and implementation of computer systems and applications. Under this stream, students learn the following: Data Structures and Algorithms, Microprocessors and Interfacing, Computer Communication and Networking, Database Systems, Internet Technologies and Applications, Software Engineering, etc.
Hope this helps.

All three are completely different. BBA is recommended, if you want to enter management. MBA would be needed after BBA. So, if you are planning to pursue MBA then go for BBA. BCA is Bachelors of Computer Applications. If you are interested in making a career in IT, then go for BCA, B.Sc can be done in IT, Computer Science, Physics, Chemistry, Maths, Biology, etc. If you want to make a career in IT, you can do B.Sc IT or B.Sc CS. I would personally not recommend you to do B.Sc in plain sciences unless you want to become a teacher or scientist. Ask yourself what do you want to do in life? What are your aspirations? Make a decision on the basis of your interests and aspirations. All the best.

As the name suggests, marketing is more related to knowledge of marketing strategy. In this course you read about cases of selling, buying, promoting and negotiating. You do comprehensive SWOT analysis of companies/strategies of companies/different products. Much importance is given to Out-of box thinking and creative ideas.
Curriculum of Marketing includes -
Marketing Research, Consumer Behavior, Brand Management, Customer Relationship Management, International Marketing, Digital Marketing, Retail Management. International Business on the other hand legal, financial and economic concepts at global level. One needs to be a careful and precise researcher as different cultures of world are in consideration. One should be well versed with the geographies and market of different countries.
Curriculum consists -
Cross cultural management, Global procurement and supply management, International Business Law, International Business Markets, International Marketing, International Banking and Capital Markets.