hello santosh panda

 yes you would be able to as you could appear for jee mains for 3 consecutive year after your 12th year so either way you are eligible for the same

hope it helps

Thanks for the question. 

Yes, you will be able to give the JEE 2019 if you get more than 75% for IIT and 60% for other colleges at least. 

The regulations change a bit but the basic point is this only. Score as much as possible 

Good luck