IISER Entrance Exam

Yes, you definitely can. There are three pathways to appear in IISER exam I. e. Either through KVPY or JEE or SCB. Since you have dropped mathematics you can either go through KVPY or SCB. So, check your SCB according to your state and then you can apply if you qualify the cut-off marks.
All the best!

Yes, you are eligible for the same.

Mathematics is not a mandatory subject for the exam. However, you need to have a certain amount of marks in your board examination to appear for the test. You can apply for IISER if you have cleared your class 12th exams either this year or last year.

Yes, you can write IISER exam after completing B.Sc.

Yes, you can apply for IISER exam.

Delhi University has its own entrance exam for Master's degree. As far as IISER is concerned, it provides a 5-year dual degree programme and not a separate Master's programme. It offers Ph.D though.

Hi Sruti,
As you are studying in class 11th, it is the best time to start your preparations for IISER. As IISER is one of the toughest exams, it will be better to give more time to yourself. The syllabus is same as class 11th and 12th. You can refer to NCERT for your preparation to clear your concepts and to make your fundamentals strong. Paper is based on your concepts only. You can make your important notes which will help you at the time of revision. You can solve as many as MCQs for your practice and complete mock test series to work on your strength and weakness.
Good luck.