JEE Main

You need to know that, in an engineering college you have to study in English, so you have to prepare in English with NCERT books.

Manav Rachna, YMCA, Lingayas and B. S. Anagpuria are some of the old and reputed colleges for CSE through JEE exams.

There can be two choices -
If you have scored a good percentage in 12th board exams then you can prepare for JEE Mains by yourself. For this, you can also refer to the study material of ALLEN, RESONANCE or VIBRANT coaching institute. In this case, you can complete your first year of polytechnic also.
The second one is, if you have not secured good percentage in 12th boards then refer to a good coaching institute and try to score good marks in JEE Mains.

Sorry, you can't do it as it requires 10+2 but you can apply for lateral entry in best college like MIT or government college without doing JEE Mains in B.Tech. it's an easier way but you can not appear for IIT.

Yes, its good to take a chance. If you clear your JEE exam then there will be no problem to get the admission. If you couldn't qualify then you will have another option without any loss.

It is IAS because it has more syllabus.

In boards exam 60%+ is better. For CSE in Jadavpur, this year cut off was about 286 rank. In short, you need to get 120-150 out of 200 marks in WBJEE.

JEE is a two stage examination, where the first stage i.e. JEE mains is conducted for admission to various engineering colleges including NIT's. JEE advance, which is second stage is admission in IITs. JEE results are not used for MBA degree.

If you want to get an IIT college, first you appear in JEE mains and qualify this exam. The cut off is nearly 105 for general and next you will appear in JEE advance and qualify under 10000 rank, then you will get an IIT college.

The cut off for general category is 100.