Yes definitely, you are eligible for all NITs as they accept only JEE Mains. moreover, you are eligible to all IIITs and Government funded Institutes as well with JEE mAIN.

The major differences between both exams have been shared below to clear your doubts.

https://engineering.careers360.com/articles/how-jee-advanced-different-from-jee-main

For most coveted IITs , JEE advanced and JEE mains is mandatory.

You can get the eligiblty criteria for JEE MAINS below:-

https://engineering.careers360.com/articles/jee-main-eligibility-criteria

All the best..!!

Yes, you will get admission in NITs on the basis of JEE Main.

NITs takes admission through JEE Main only. To get admission in IITs you have to appear for JEE Advanced exam.

Make sure you get 75% marks in your boards exams or you should be in top 20 percentile to be eligible to get admission in NITs in general category.

Good Luck!!