JEE Main

Based on your WBJEE rank, you can expect seats in Techno India Salt Lake Institute, same link can be used to check eligibility for Heritage College. Branch choice should be based on your field of interest. Looking at current trends, IT companies are offering jobs in great numbers so Computer Science and Information Technology will be good option to look. But before making any choice, do consider your field of interest.

Yes, you can do B.Tech CSE but you will not get any government college. Don't lose hope because of your rank. You can apply in private colleges. You can give entrance exam as well. Find the cut-off of previous years. Surely you will get admission but I will suggest you to do well in your B.Tech because this is not a good score. Don't lose hope. Give your best.
All the best.

I will answer your query about film direction. Jamia Milia Islamia is one of the best Institute in Theatrics and Visual Arts. Many bollywood and documentry writers are alumni of the institute. Also, in my opinion, 89 marks are good but being in General Category increases the level of competition and hard work. So, if your son is not interested or is reluctant please don't force him.

It will be difficult to get top IITs/NITs/IIITs at this rank. Other colleges you may expect like Tezpur University, Sant Londowal Institute of Engineering and Technology, Institute of Technology Guru Ghasidas University, HNB University. Check the below link for courses you may expect in these institutes-
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor.

JEE Mains is for B.Tech and BE colleges only. Diploma exams are conducted by State Technical Board.

Without doing registration, you cannot get admission in any reputed college.
But still, there are some colleges which take direct admission.

Hey buddy sorry to say that but you cannot get MNIT with these marks as you do not have 75% in class 12th.
You are not eligible for NIT's. Try for state government engineering colleges.

Hi buddy,
See the eligibility criteria of JEE, you cannot replace compulsory subjects. Candidates must have to take minimum 5 subjects in 12th/equivalent examination. Candidates appearing for JEE Main 2018 must have passed class 12th with Physics & Mathematics as compulsory subjects along with one of the Chemistry/Biotechnology/Biology/ Technical Vocational subject.

I think you should go for UPES, although fee structure of upes is very high. You cannot get any NIT with these marks. One most important point is that upes is not good for CSE.

Friend, there is no chance of getting NITs or IITs. You can get state government colleges or you can go for other private colleges available.