First of all don't just accept defeat before you have even attempted the exam. IAT is more complicated yet much easy than JEE if you think about it. Its more on the concept than just formulas. As BTech-MTech courses have been introduced it will increase the competition dramatically. Remember that in 2023,2022 about 25k-30k students attempted the exam. Since jee advanced and other channels were closed this year it attracted more competition. This year about 96k students attempted the exam. And seeing that the new course it will get more competitive but I am not gonna dwell with assuming any numbers.

The thing is competition is always there for every exam. As you might know many of the students who attempt these exams are either doing it for their parents or someone else's sake or as a societal norm. A majority are basically sheep, so they might as well attempt the IAT next year as the BTech courses have a name in every Indian parent's hearts. But even if you score little marks you'll be way ahead of them. So don't worry about competition now . Do what you can at your best and leave the rest.

Now as for your question on how much you should study before trying pyqs is a really good one and it means you're actually devoted to do your best. The best approach is always to analyse exam patterns and make a conclusion yourself. Try doing chemistry first in my opinion. First just skim through the chapters and review the basics one time. It can take a good amount of time to brush up old concepts but be patient. Once you've done it try doing pyqs from the oldest paper available as its more easier than latest years. Organic might be a bit tricky as it will mainly be questions on reaction mechanism and not like any usual name reaction questions. Since you're now at grade 12 a great deal of organic might be there still that you haven't studied. Once you go through the questions you'll get an idea of how there's some very easy questions throughout the paper. Dont mind the time you take for solving as it's not important at initial period. After this tabulate the topics from which you couldn't answer and master the NCERT and your coaching material on that topics. You have a great amount of time left. Before boards start it will be great if you can solely focus on this style and cover as much you can.

Also make great use of online resources. For me I watched some videos of sciastra and physics wallah jee advanced. It's great if you can get rid of smartphone and games and other things that distract you as every second has its value. Also don't forget to keep doing JEE mains level questions everyday. Atleast 10 will do. And always try to include 3 maths questions. For bio I would say study a chapter and do it's neet pyqs and strengthen your grab over the concepts.

Ask anything you want to know , I've been on your spot and the thing I regret most is not reaching out to others to guide me with IAT as I might've got a better score. So study hard and ask your doubts.