NIT

Hello Samarth,
Please specify your category so that I can suggest you better, however, you may refer to this link for more insights:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

Go to the rank predictor on Shiksha's website and find out your rank. After this, it will easier to predict whether you will get in or not. And it is also dependent on cutoff marks of JEE 2018.

Yes, you may get admission in an NIIT, but it won't be any of the top NIts.

No, NIT does not offer lateral entry. They enrol students for regular MCA programme through NIMCET exam, details are given below:
https://www.shiksha.com/university/national-institute-of-technology-durgapur/exams/nimcet

Chances are high though wait for exact ranks to get confirmed. You'll get admission in B.Arch course through this rank.

With 50000 as your rank and having OBC category, you will surely get options for many NITs. You can choose the college and branch when you get exact rank. All the best.

Chance are less, but it all depends on your OBC - PWD rank. You may get some new NIT with non-core branch. All the best.

DTU along with NIST falls under JAC and NIT falls under JoSAA. Therefore, both have separate counselling mechanism.
There will be a common merit list for DTU and NSIT prepared by JAC.

It depends upon the cutoff which has not released since the result is not announced. The result will be coming on 30th April 2018. After this the cutoff for the different categories will be announced. Then if you do not attain the minimum score then you will not get any college but if you have qualified with above minimum marks then it might be possible that you will get the college.

Yes, you can get NITs but not the core branches such as CS, mechanical, civil and others. You will get another branch of your choice.