BCA

B.Sc IT has more emphasis on theoretical concepts of computers Science whereas BCA syllabus emphasis is on application development. Thus BCA is more practical oriented in majority of universities.

Indian IT industry is in decline phase. No. of new jobs being created are reducing day by day because of outcry against outsourcing in Western countries. Most of the freshers recruitment is by campus placement. If you do BCA by distance learning, you will miss out on campus placement opportunities and may struggle to find a job. Therefore, you are advised that you should do BCA only from a prestigious formal college with good campus placement records only.

Delhi University B.Sc CS is a better option in comparison to run of mill BCA colleges. DU brand name will provide you advantage through out your career particularly in initial stage of professional career.

If you want to appear for Civil Services Examination, you can choose any subject of your preference in which you are confident of excelling. Civil Services exam is very tough with limited seats. Therefore, you must chose your subject carefully. Nowadays, most of the civil services aspirants go for engineering so that they have an alternate career available if they are not able to crack Civil Services examination.

B.Tech is a technical degree that will give you training on software,design, implementation, and management of information system of both software and hardware processes. B.tech IT deals with installation, development and implementation of computer systems and applications. Whereas BCA is all about applications. It depends on your interest and skills to find which is better for you. B.tech though has more value any day than BCA.

Yes, there is a major difference between BCA and B.Sc.
BCA is a Bachelor degree for computer science and you can get a job as a programmer by this field. Many programming languages are introduced in BCA degree.
The other one B.Sc is the Bachelor degree of science and you can also choose B.Sc.(computer application). It's also a good idea.
But, in my opinion, BCA is a good option for future preference.
So, all the best for your future.