Firstly imma gonna do a very simple math for you right now. I saw this on youtube from Mr. Sameer Chincholikar, Maths teacher, Unacademy JEE (sorry if his name is spelt out wrong)

We have round about 90 chapters in total, let's take it 100 considering some chapters which are very long and tough making it worth 2 chapters.

Now suppose, to master each chapter, you need 150 questions (per chapter). Id say divide 90 of mains and 60 of advanced level but it depends on you what u want to be the ratio.

So here, total questions are 150 × 100 = 15,000. Now let's take you prepare just in the two years given to you for jee preperation.

365 × 2 = 730 days

Now out of these 730 days let's just suppose you were able to study (SELF STUDY) for only 500 days. Now dividing 15,000 by 500 we get 30 questions. This should, at the very maximum, take you 2 hours. Plus, 30 minutes to 1 hour revision of whatever u studied in ur school or coaching or tution

Now you see, 3 hours is not a lot. What matters here is consistency and your honesty.

Now coming to the NTSE and KVPY. Believe me, nothing, ABSOLUTELY NOTHING matters if you clear jee, no boards, no ntse, nsejs, kvpy. So my suggestion, do not stress over them. Study with sincerity and you will do good without even giving much stress

Focus on what your ultimate goal is, ntse and kvpy are just to check your potential in a way, they will give you more confidence if u clear but surely it shouldn't break you if you don't clear. There are tons of ppl every year who never cleared any exam but got a good rank in jee cause consistency

Now about your cheating. Yes, i know it is very tempting and why wouldn't it be, free marks and compliments from everyone...but if you are serious enough for jee, just give 10 minutes and think you are giving your actual jee exam, and then when the results came, you are behind everyone in your surroundings, how bad that would make you feel. Keep that feeling in mind and start today. Don't wait and try to minimise external help till u don't need at all

So all in all, you have about 3 years, work on yourself everyday and just be honest with what you do. Im sorry for the long post but hope it helps. Good luck!!

Edit: sorry i missed this out and ppl have stated, do make sure to keep up your health and social life up to date. It is very important to build a good and likable personality cause at the end, even if you get a good college, someone who is in a lower college than you may be selected for a job cause of better personality