BSc Data Science focuses on statistics, big data analytics, machine learning and related aspects which make you understand the problems/phenomena with respect to a set of real world data whereas BSc IT revolves around the processing and management of information in a systematic way through the subjects technical communication skills , data structure using c language, content management system, etc.
So you can have a rough idea about the two courses but which one is better is something only you can decide as you will know better which subject interests you more.

It depends upon the JEE Main and JEE Advance cut offs, If You manage to qualify the exam by achieving the cut off, You can apply for JOSAA Counselling. It should be noted the cut off for EWS/SC/ST/FEMALES/OBC category is lower than the general category

If you manage to qualify JEE Main Cutoff, You would be eligible for JEE Advance which is the intake exam for IITs as mentioned above.


However It is usually advised to fill the choices as per the preference of colleges and departments, for example CSE in NIT Trichy is your priority followed by CSE in NIT Warangal, you can fill CSE at NIT Trichy at serial number 1 and CSE at NIT Warangal at serial number 2 and so on and so forth. However to get any NIT, you must have qualified JEE Mains and to get any IIT, you must have qualifies JEE Advanced

But the previous cut offs of colleges should be taken in consideration, it is better to research over the cut off of colleges then make a preference list of colleges and fill accordingly

For the college preferences and the courses provided by these colleges and to know which colleges participate in the JOSAA counselling, please go to the below mentioned link: https://engineering.careers360.com/articles/josaa-participating-institutes/amp

For college prediction as per your marks and rank, please go through the below mentioned link: https://dqxeclau.top/college-predictor

Rest for information on any particular college, you can dig their official site for better information

The process through which branch change happens here at IIT  is as follows:(for 2018 and 2019 batches)

First the grades in courses MA1101 and PH1010 are considered. Then in case of a tie(which almost always happens) the GPA is considered.Thus a priority order is created.

Some important rules are that 1)only net 10% students may add to the branch 2)only 10% students may subtract from a branch.

This means ; say EE has 130 students ,10% of which is 13. But say if 2 EE guys go to CS, then 15 can enter EE.

But the most interesting rule is as follows

Consider a student from Biotech wanting to shift to EP. Let's say he has a GPA of say 8.9 with a A grade and a S grade and is listed in priority order with rank 29. Also EP has not satisfied its 10% branch change quota.

But owing to his bad luck , he is not able to be in the top 10% cgpa holders of the biotech department (who are eligible for branch change) which rules him out of the branch change race.