hey,

i hope you are doing so well , so you are asking about AIEEE exam then first let me know you that after 2013 AIEEE exam is known as JEE mains ,however both are same there is a variation in name only , to get admission in IITs you are required to clear the both JEE mains and JEE advanced

talking about eligibility than a diploma student can give JEE  mains exam to get eligible for JEE advanced , no diploma candidate get admission in NIT , diploma candidate can get admission in IIT only and for this you need to clear both the exams

good luck!