Hello,

First of all, to take admission into BCA (Bachelor's of Computer Application), you don't need to pass out 12th from Science stream. If you had Mathematics as one of your Subjects then you are eligible to pursue BCA course. Now, B.Tech is an engineering course (Bachelor's of Technology) and it is little advanced as compared to BCA. But MCA (Master's of Computer Application) is a Postgraduate level course. But B.Tech includes lot of different streams like Civil, Mechanical, Computer Science and Engineering, Production, Biotechnology, whereas BCA focuses only on Computer Education.

You can do B.Tech even without appearing for JEE MAINS. But you won't be able to do BCA from Institutions like IITs, NITs, IIITs, and GFTIs. Remember, You will have to appear for other state level or University level exams to pursue B.Tech course. Most of the Universities considers JEE MAINS score to offer Admission into B.Tech. But in Universities like VIT (Vellore Institute of Technology), admission into B.Tech is not based on JEE MAINS score, you have to appear for VITEEE (Vellore Institute of Technology Engineering Entrance Exam) to pursue B.Tech from VIT.

Good Luck.