Hello dear, 

The eligibility for jee mains is given below: 

• Candidates must have passed class 12th or qualifying exam. 
• Candidates appearing for class 12 exam or equivalent exams are also eligible
• It is compulsory for candidates to have 5 subjects (language, physics, mathematics, chemistry/biology/biotechnology/ technical vocational subject, any other subject) 

And for the admission in NITs, IIITs, GFTIs the following will be considered while admission: 

• Candidates must have secured 75% in class 12th or equivalent exam. 
• Candidates belonging to SCs/STs should secure 65% in class 12th or equivalent exam. 

That means, you can appear in jee but for admission in NITs, GFTIs, IIITs you must have 75% (general) or 65% (sc/st) 

All the best!