Delhi University (DU)

That is a very tricky question. Most top colleges cut offs are in mid-90%. So, you do not have the chance to get through in top colleges. But, for some courses DU cutoff's are less (not sure which subjects you are looking for).
Otherwise, there are many more options - JMI University is best, IPU is reasonably good.
Besides these, you can opt for private universities in Delhi NCR.

Try IGNOU. There are many distance providing institutions in India.

Since you have completed your class 12th with 86% marks, so getting SRCC is not possible, but you can definitely apply in DU for UG course. There, all you need is to fill up an admissions form, then you will be shortlisted according to the college cut off list.

Apply in Delhi University.
They conduct entrance exam also.
But, if you have very good percentage like 90+, then apply for merit based entrance.
Good luck.

You should opt for B.Sc in chemistry.
Good luck.

It is typical to confirm based on marks, firstly predict your rank. Please go through this link & predict your rank.
Rank predictor : https://www.resonance.ac.in/answer-key-solutions/JEE-Main/2017/jee-main-2017-rank-predictor.php
Eligibility predictor: https://www.resonance.ac.in/answer-key-solutions/JEE-Main/2017/jee-main-2017-eligibility-predictor.php