BCA Preparation

You can take admission for BCA after 12th, some of the universities take entrance exam and many take direct admissions. For entrance exam the main BCA Entrance subjects include English Mathematics, Analytical skills, Reasoning skills, General awareness skills, and Basic Computer knowledge.

You can get an idea of the eligibility criteria of IMS Ghaziabad UCC for BCA admission from the link as mentioned here https://www.shiksha.com/college/ims-ghaziabad-university-courses-campus-49334/course-bca-diploma-in-data-science-265689 and apply accordingly.

Hi, BCA is a graduation course. Since, you have done class 12th, you may now take up Bachelor of computer applications in a leading college and hence obtain the degree. It is a 3 year degree. You will need at least 45 % marks in class 12th and you can take it up.

Some good books for BCA entrance exam are mentioned below-
BCA Entrance Exam Guide by Rph Editorial BoardBookhive BCA Entrance Examination Guide by S.L. Gulati & Sanjay Kumar SharmaBCA Entrance Examination by E. DharamrajBCA Entrance Examination by Expert CompilationsBCA Entrance Examination ( Popular Master Guide )by R. Gupta's

I'd suggest against taking up engineering if you're not sure of what you want to do, because it's a rat race out there, and you'll regret it later. I'd suggest you choose between the other two.

Hi Sneha,
You can prepare for GRE along with your studies or even after. The GRE is not taken to apply for jobs, it is taken to pursue Master's degree programs in US.

You are eligible to appear for Civil Services exam after BCA.

For BCA you d at 12th level , but why you want to change your field from medical line