NIT

Yes, definitely you can get admission in NIT or IIIT.

If you are in general category, then you can get admission in NIT College. But, if you are in reserved category may be you can get admission in NIT College.

Hi, your admission to NIT will be done by Central Seat Allocation Board which gives score by that 40% boards + 60% JEE Mains. They will give rank list based on this scores according to which you'll be asked to fill up your choices (NIT's plus some additional Pvt. Universities). I think you have some chance to get admission here but due to less marks in boards, you loose these chances. Don't worry and try to apply for these. I hope you understand.
Thanks.

Hi,
It is totally dependent on your caste category. If you are from general or OBC category, then it is impossible to take admission in good NIT or good IIIT. But, you have chances for admission in mediocre or low rank IIITs. But, You can predict your college based on your rank in JEE Mains in given below link :-
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

Yes, you can get admission but it all depends on your spot round counselling.

There is a very less chance but yes, you can try in spot round.

You can apply for NIT Trichy or BIT Mesra.

Yes, for sure you can get admission in NIT, but the only problem you can face is for a dream branch and good NIT.

It will be tough with that. Though you have excellent board percentage, I would not recommend you to go in NITs with lower marks as you'll only get that with 104 marks in JEE being from General. Though, you can go for NIT Silchar, Pondicherry, Manipur and Surat with mining and metallurgy or B.Sc. courses in them.

Yes, there are 90% students in NITs who opted for CSE and are studying it for the first time. There is no problem with that.