Career

None of them answered your question correct. So, at first about the placement: No IIT's have got 100% placement but only those opt for campus placement which is around 60%-70% of the total eligible candidates. So, you can't be placed if you don't opt. So, I don't see a problem in placement in IIT here. So, don't believe those misinterpreted placement statistics in your newspaper. (Note : My words are coming from the official placement data published by IIT Bombay. )
Now, about IIT or IIST. You should go to IIT if you wish to continue your study and do M.Tech or Ph.D. as when you apply for higher studies the IIT name will give you an edge all over the world. I know that IIT's don't have good ranking on those lists but trust me people know and admire them (I have read about it on Quora that many of students say that many of their best batch mates were from IITs, Stanford, Harvard, MIT students. Sundar Pichai would be the most prominent example). Now, if you want to do job after B.Tech then IIST is better as you get a job in ISRO/DRDO directly but bear in mind that only those who score best in all 8 semesters will get a job with more that 7.5 gpa in each semester, which means that just getting more that 7.5 gpa won't ensure you that job and if you score less than 7.5 you are not eligible (you won't get kicked our something as someone answered. Nope, you have got plenty of other options. )
Hope it helps and that I cleared all the doubts and wrong answers which were given. If not then ask your question in comment section. And best of luck for your future.

The Indian Council of Agricultural Research (ICAR) is an autonomous body responsible for coordinating agricultural education and research in India. There are 75+ state agricultural universities, 5 Deemed Agri Universities and hundreds of research stations under the ICAR, which are working towards the meeting the goal of Education and Research in Indian Agriculture. At graduation level, there are 10 major courses offered at ICAR affiliated universities/colleges. (Agriculture)B.Sc. (Horticulture)B.Sc. (Forestry)B.Sc. (Sericulture)B.Sc
B. Fsc. (Fisheries). (Environment Science)
B.Tech. (Agril. Engineering. )
B.Tech. (Food Technology)
B.Tech. (Dairy Technology)
B.Tech. (Biotechnology)
Now, all above courses are having its own specializations. So, it depends on your interest, college/university at which you got the admission, that which course is best suited for you. On the basis of the number of colleges and job availabilities, (Agri), B.Tech. (Agril. Engineering), (Horti), B.Tech. (Food) these are some popular courses.

You can join some research organisation, or companies into research, or clear GATE/NET and join Ph.D. with a good lab. Also you can join for as a JRF in a lab and enroll for Ph.D. Next best option is to take up a course in clinical research/ medical coding and getting yourself employed more rapidly. Both the industries pay you handsome salary. Actually the former is the equivalent of IT jobs in our industry. There is a lot of scope and if you dedicate yourself properly in a decade you will find yourself in a great position career wise and finance wise. The next best option is to identify a problem and solve it through a start up.
Also, if your college/ university as an incubator scheme apply for it. They will know you better and assist you accordingly.
All the best.