B.Sc

You are advised to start your self preparation now and then opt for one year duration coaching for CAT 2018 starting in Nov Dec 17. This will give you sufficient CAT preparation time without impacting your B.Sc studies.

Yes, you can pursue B.Sc in nursing.

Suraj,
For you, I would say that marks really don't matter to judge your intelligence, but coming to the admission section it really matters a lot. Now, since you have got 60%, I am guessing that you are a CBSE board student. Sorry to say, but if you are hoping for top government colleges, you may need to face some disappointment. You can get admission in a private college very easily (of good reputation).
I hope, I have been able to help you.

Hello Jaswinder,
You have managed to score very well in your boards and JEE Mains. So, you should go for B.Tech only. However, considering your score, you will easily get colleges like LNMIIT, NMIT, Thapar Univ. and JIIT-Noida. You may also get lower NITs in the last phase of counselling. Check here for more insights.
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

IAS and B.Sc computer science are both different subject. Preparing for IAS involves lot of general studies and also you can choose one specialization after the preliminary. It's just a matter of fact that both the subject are not related too much. Any graduation is required for writing civil service.

Hi Akshay,
I actually don't know about the college you mentioned, whether it's good for B.Sc in physics or not. But what I know is that St. Xavier's College, Kolkata is really very good for that particular course. Presently, SXCKOL is the best college rather an institute under UGC all over India with a score of 3.77 out of 4 and I am not saying this, it's according to the NAAC.
All the best.