Test preparation

Go through the marking scheme of the examination and prepare the chapters which contains large marks. This will help you secure good marks.

No you can't do it because in CA you must having commerce background that means 11th and 12th are in commerce.

Yes, proper preparation with proper strategy will make you crack the exam. You can achieve whatever you want just make a proper way to get it. First of all, go through the syllabus of CAT 2020 then start preparing for only those topics
https://www.shiksha.com/mba/articles/cat-2020-exam-blogId-25095.

Hi. There are various M.Sc. Food and nutrition entrance tests, so please mention the test you're referring to, to know the exact syllabus. Some books that will help you to prepare for almost all tests are-
Food and Nutrition by Dr. M Swaminathan
Objective Food Science by Sanjeev Kumar Sharma
Food Science by B Srilakshmi. All the best!

So what do you want to know about it tell me and I will tell you all about it.

Candidates are advised to pick only those CMAT books for preparation that are as per the latest CMAT 2022 exam pattern and syllabus. Check CMAT Syllabus 2022
With hundreds of books available in the market for CMAT preparation, candidates are bound to get confused on which book to select. Hence, they must refer to the most recommended books for CMAT preparation by renowned authors like Arun Sharma, N K Sinha, Norman Lewis, and others.
Check CMAT Previous Year Question Papers
CMAT 2022 exam is expected to be held in March 2022, hence candidates must grab the best books for CMAT for revision and practice.

No, now it is not necessary because DU LL.B. HONS is after graduation. So you should focus on class 12th first. If then also you have time so first start preparing for entrance of graduation of University you will be going. I think this is enough for you to understand.

The simple answer is to read NCERT as much as you can.

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.

Refer the following:
https://www.shiksha.com/bba/set-exam-preparation
Thanks.