Yes you can definitely attempt the Jee Mains exam in April. The best of the two marks will be selected as the final marks in your result. So you need not worry about it. So you are free to attempt the exam again. You have also got 3 chances in total to attempt the Jee Mains exam.

Yes definitely student can appear for both JEE main session that is JEE main January as well as JEE main April. those who appear for both the best of the two normalised score will be counted for the rank calculation, the registration for JEE main application will begin from February 8th onwards.