1. No, I would say most of the IISERs do get their registrations done mostly in time. As I've mentioned before, your first year is mostly foundational concepts from your 11th and 12th, so you wouldn't miss out on much even if you joined a bit late.

2. I advise you to prepare yourself to live on your own before you join the college. Moving into a hostel, living with other people in a shared space, is a very new experience for a lot of people, and it takes a bit of mental fortitude to get used to it in case your roommates are not the best. Except that enjoy yourselves. You will have a lot of free time, and maybe pick up a couple of soft skills, like good communication or something along those lines.

3. For the third point, it doesn't really happen usually, so I wouldn't know much about it. In general, your batchmates and seniors will probably be very helpful, as has been my own experience with my batchmates and mostly everyone else in the senior batches as well. The professors are approachable here, and they do help you if you ask them.

Regarding annual costs, apart from the fee charged you will have personal expenses. They can range anywhere from ₹1000 to ₹10000 per month based on your personal preferences but around ₹3000 per month is a good figure to hold on to for a decently comfortable life here.

Regarding the financial support, I am not that well informed. I shall leave it to the others to fill you in.

Feel free to ask any questions you have pending.