can we get through NIT, JUST by studying IIT IN 12 STD ALONE??

Hello,

It will be helpful if you start preparing when you are in 11th standard, you will have sufficient time by the end of 12th standard. When you are in 11th standard you don't know the 12th syllabus so all you can prepare for JEE main is 11th standard syllabus. So if you start studying from 11th standard, you will have good amount of time to prepare for 12th syllabus. But it is also okay to start your preparation in 12th, but this may not bring good results and you may end up panicking. So to be on safe side it is best to start from 11th standard.