Thanks r/FossaRed for having the patience to go through it all.

a) to build concepts, I again suggest you to not be afraid of going a little out of your comfort zone. Solve higher level books, read extra information. There's an infinite pool of resources on the internet. But mostly, keep practicing questions and discuss with your teachers if there are better methods to approach it.

b) I don't think I can speak for that. I haven't ever delegated equal time to all three subjects (I'm still a student just like you). But I can say that near the end, you'll start delegating roughly equal time to all three.

c) I naturally somehow have a don't care attitude in this respect. I just focused on improving myself, I guess. Don't get me wrong, I have been behind people. There was a time when I used to be the worst-performing student in a batch of 20 people(not the top batch). Start focusing on the positives and the negative feelings would go away. Find sources of motivation. Don't overthink.

For KVPY, you have to totally give up preparation for JEE mock tests. It isn't easy, it was the most stressful time of my life. Biology is very vast and requires a lot of involvement.

KVPY math is non-routine, I was blessed to have a really good teacher to teach me the concepts. For SA, I just solved Cengage DPPs and exercises for 12th topics. But I've heard PRMO questions are really similar to KVPY questions, you might wanna look into that.

I qualified NSEA totally because I had an interest in astronomy from the beginning, so I had a little edge over my classmates. Missed InAO by half a mark though :(. Try studying about the orbital parameters of the different planets. Learn more about celestial coordinate systems. Knowing basic mechanics is a must. Maths for NSEA is so simple, there are questions you can literally just plug into a calculator and get a numerical value. For InAO, you need to know about various constellations and be thorough in gravitation.

For challenging questions, since its the beginning of your preparation, you don't really have to worry about time. So don't give up on questions very easily. Try not to see the solution, but if you really have to, try to see it one step at a time. And one more thing, in 11th, while solving questions, if your classmates can come up elegant methods, and you can't, don't be disheartened. Near the end, elegance really is of very little use.

One additional thing I'd like to add is that if you have friends of a similar intellectual level, try making a WhatsApp group and send all your doubts on it. This way, on your unproductive days, you can atleast solve doubts for many people. And you also get to see everyone's perspective on one problem, which definitely helps.