JEE Main Scores

Yes, there are full chances of getting CSE in NITs. You must have to participate in counselling of JEE. Only after counselling, we will get to know about fees concession.

Bro, I suggest you to take admission in any one of your nearest colleges. And do hard work in the computer field that is, learn programming languages and try to make projects based on them. After some time, you will get to know about how companies are doing their work.

Sorry, but you will not be able to get into Nirma Unversity with these marks. Though the selection is dynamic and dependent upon the students applying for it and hence changes every year, still the cutoff for CSE/IT is around 2k and the least non-technical branches is around 80k.

There are good chances for getting a government seat.

You can look for state engineering colleges accepting JEE Mains score. If you want to pursue engineering from IITs/NITs only than you can also go for one more attempt (if its your first attempt). If you want to do engineering than go for a state engineering institute and work hard. You can try for GATE and again look for IITs/NITs to complete your M.Tech. Just be determined towards your goal. Best of Luck!

As your rank is not good enough to get such colleges which is best for CSE through JOSAA.
Go to such colleges which offer their own test and counselling for admission.

Sorry, but with this Marks in class 12th, you will not be able to get any IITs and NITs. May be you can get Government Colleges or you can go for Private Colleges. To know more about Colleges on the basis of your Marks and rank:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor
You can go for other courses like B.Sc. BCA integrated courses and more.

You cannot get any NIT or IIIT but you can get some private colleges through the Jossa or you should try with the state counselling for private colleges. You can also go for IPU, Nirma, Amity, Chandigarh University, JECRC, etc.

How can one answer this question? No one can answer this question. Data is not given like that. You can only know the last year's cut-off, percentage qualified in each state, general rank or category rank. This type of data is not given by JEE or CBSE. So, don't believe if anyone answers this question. Cut-off will be near to the last year for your home state.

As you know, every student works hard but toppers have a different strategy of smart study which differentiates them from the crowd. The secret of getting more than 250 marks is focusing on those topics which are not asked or very less often asked in the paper. Secondly, revision of topics and paper solving
Thirdly, giving mocks. Do these things and surely success will be yours.
All the best.