Hello Sanjay,

Yes, ofcourse you are eligible for JEE Mains examination. But you cannot join NITs or CFTIs. After qualifying in JEE Mains you can appear for JEE Advanced and can get admission into IITs based on your score in JEE Advanced.

JEE Mains is just to get the eligibility to write JEE Advanced exam. Diploma candidates can get admission into IITs.

For more information go through below mentioned link.

https://engineering.careers360.com/articles/jee-main-2022

To get more information about JEE Advanced eligibility criteria go through below mentioned.

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

I hope this information was helpful to you.

All The Best!!