Hi Ankit. Thanks for contacting Careers360 and we hope we will be able to answer your query. 

Note that one can give JEE Mains thrice (but no one gives the attempts twice). But that should be in three consecutive years. That means if you completed your 12th in 2018, you are eligible to give JEE Mains of 2018, 2019, 2020.

I would also advice you to look at this PDF for more information:

• https://www.google.co.in/url?sa=t&source=web&rct=j&url=https://jeemain.nic.in/WebInfo/Handler/FileHandler.ashx%3Fi%3DFile%26ii%3D88%26iii%3DY&ved=2ahUKEwiguumA7YTaAhUKv48KHeRLDFIQFjAIegQIABAB&usg=AOvVaw2wtF0peVNYjFAK9Mblnxy_

Hope this helps you and all the best!