IIT

For pretty obvious reasons, only the marks you get in IIT will be given weightage when an interviewer is hiring, just like while giving admission into IIT you are not asked about your marks in primary grade.
The recruitment procedure depends mostly on the interview you give and the technical skills and knowledge you possess. However, your CGPA in IIT helps you in getting to the interview as in the per-interview selection candidates with low CGPA are mostly screened out.

For admission in NIT, you should have a rank within 10000. So, it is not possible.

Don't go on assumptions, just match with the answer key and if right then prepare for JEE Advanced because previous year's cut-off for SC category is 52.

No, without clearing these entrance exams, you are not eligible for any government colleges according to the new education policy.

Yes, you can but before that you will have to crack JEE Mains and then JEE Advance.

Hello Mohit,
If you have not appeared for JEE Mains then IIT and many CGFI including NITs are out of the way. If your state is accepting JEE Mains score then that too is gone. I think your best chance is with few of the private colleges which admit students based on their own CET.

B.Tech from IITs is best after 12th from Science stream.

From this year, class 12th marks will not be considered for JEE Mains. You may get NIT of North-East states but I would advice you to rather keep preparing for JEE Advance from now itself.

B.Tech from legacy IITs have more scope in comparison to law degree. IITians are granted by both Indian and International firms. B.Tech degree from a normal college has scope similar to law degree.

Hi,
You may refer to following article for tips on cracking JEE:
https://www.shiksha.com/b-tech/articles/10-tips-towards-your-jee-mains-advanced-preparation-blogId-11721