Dear Venkateswar Nayak 

I am afraid there is little you can do in this given that you are not eligible to appear for SB Stream of Kishore Vaigyanik Protsahan Yojna (KVPY) scholarship scheme in the first place. As per the eligibility criteria of giving KVPY exam under SB stream is that you should enrolled in the first year of an undergraduate program in one of the basic sciences subjects including Physics, Chemistry, Biology and Mathematics programs mentioned below. Since you are not, you are not eligible for the award of the scholarship. 

Subjects Allowed (for SB Stream): B.Sc./B.S./B.Stat./B.Math./Int. M.Sc./Int. M.S. in Chemistry, Physics, Mathematics, Statistics, Biochemistry, Microbiology, Cell Biology, Ecology, Molecular Biology, Botany, Zoology, Physiology, Biotechnology, Neurosciences, Bioinformatics, Marine Biology, Geology, Human Biology, Genetics, Biomedical Sciences, Applied Physics, Geophysics, Materials Science or Environmental Science are eligible for KVPY fellowship.

As far as attending the interview is concerned, the website clearly mentions that no candidate without the relevant documents will be allowed to attend the interview. Study certificate signed by the head of the institution (of current institution) is mandatory. 

At the maximum what you can do is try to go to the interview and try your luck there. Tell them you will get enrolled this year itself. But, since it is their basic eligibility criteria for SB stream that a candidate should already be enrolled in the first year of a basic science undergraduate course, it is highly unlikely that any leeway to you in this regards. 

If it doesn't workout, you can try for it again next year when you will be enrolled in undergraduate course. 

Good Luck!