JEE Main

Hello Shubham,
As per your marks, your chances are there to get some NITs, however, check here to get more details.
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

JEE'18 will improve your standard even if you crack it or not. But if you prepare for it, you can have some basic standard which you can prove during your job exams. so better prepare for JEE'18.

No, you cannot get admission into any of the colleges through JEE counselling because you need to have at least 75% in your board exams (overall) and an aggregate in PCM should also be at least 75% and also, your score in JEE mains is also a little low to get admission in any NIT, IIIT or GFTI.

You will get the admission, but you need to wait till the 3rd round.

Hello Dhruv,
As per your MHCET score, you will definitely get very good colleges, so look forward for it only via JEE Mains as you will not get any good one, however, check here for more insights:
https://www.shiksha.com/b-tech/resources/mhcet-college-predictor

Yes, the ranks for JEE main and that of JEE Advanced will remain the same for JoSAA counselling. You need to choose your category and then you should see you rank.
The link below gives you the previous year closing and opening ranks for each NIT, IIT, IIIT and GFTI:
http://josaa.nic.in/Result2016/result/OpeningClosingRank.aspx
You select your category and then the type of institute then you can see the data for 2016. The official closing and opening ranks for this year have not been released.

No, you should have more than 75% marks in class 12th boards or you should be in top 20 percentile.

No, seats are allocated on the basis of your preference. Please put your choices on the basis of your preference (higher preference first) for desired results. If you prefer CSE then put CSE on 2nd choice and after that civil on third choice.

You can check the opening and closing rank for general category by doing some Google Search. I think you have less chances but don't lose your hope and hope for the best.

It is not easy to get MITS B.Arch in 20000 rank. You should apply for counselling I think you should get.