Indian Institute of Technology, Delhi

To get into IITs you should get through JEE Advanced. With your given percentile I wish you would get into any IIITs.

I'll prefer you to opt for the IIT, Hyderabad or DTU as these are the best college from all the colleges that you have mentioned above in terms of placements, infra and faculty. You should opt for the CSE in whichever college you are getting that.

Yes, you can easily get admission in this college with this score and under SC quota.

It depends on the level of colleges. If you are trying for IIT, then above 75 is must! You wouldn't get nice colleges below 70%. Try to score your best. 50 - 55% is the minimum to get admission.

Please visit this site-
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

As there will be two JEE Mains exams this year, so after first exam only the percentile has been released right now. However, after the second exam that took place, everyone will know their ranks on the official website only. Thereafter, the marks needed to qualify will be disclosed after the second exam result that took place in this April.

Yes for biotechnology eligibility criteria is you should have physics, chemistry, biology in your 12th and for admission in IIT, Delhi you have to clear JEE exam.

Yes, you can get IIT, Delhi if you have a good rank.

Hi,
The marks required to get admission will be a very tough thing to tell, as admissions are rank based and the marks fluctuate every year both in percentage as well as absolute due to varying difficulties of the JEE each year. You can check the relevant ranks and other data on JoSAA website. It is the most reliable resource as JoSAA is the body that sees the admission process through JEE. http://josaa.nic.in/Result/result/OpeningClosingRank.aspx.

You must have rank under 100-150 in your category(ST). Score stats are different every year since the paper pattern is not fixed. But you should have scored atleast 45-50% marks for that.