B.Tech

As you are asking for Sharda University for B.Tech, I would say it is the worst college for CSE. There are many better colleges than this.

I appreciate your sense of approach. Answering your question. Changing a branch is up to you my friend (my personal opinion is to not to change the branch).
But before you opt for another branch, keep an eye on various subjects and your interests upon the subject. It's your future and your own life. So, you should be aware of your interests and take a branch according to your interest. Talking about your preparation which you did in these 3 years, it doesn't mean the struggle you had is useless. Remember, every experience gives you the new technique and new ideas. So, never lose hope and keep trying.

Kindly visit this link:
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.shiksha.com/b-tech/colleges/b-tech-in-mechanical-engineering-colleges-india&ved=2ahUKEwiv4ODYvabcAhUGK48KHQCOAwYQFjAFegQIAxAB&usg=AOvVaw1bQRcWfkW7ldFLA7hBOlry

Hi,
For B.Sc specialisation details, you can see the below link:
https://www.shiksha.com/science/articles/amp/what-is-bsc-course-all-about-know-the-full-form-eligibility-scope-blogId-13262
Hope this information will be useful for you.
Thanks.

Yes, there is an option of lateral entry in the second year after Diploma.

Hello Raushan,
Yes, you are eligible to get lateral admission in engineering after the completion of your Diploma. How you got admission is of no relevance. What matters is how much marks you have obtained in Diploma.
Best wishes.

5 rounds of counselling.

Yes, you are eligible to get a degree.