sir I have got 99.65 percentile in 7th Jan 2nd shift is it necessary to write April mains
HI Kishore,
99.65 is an extremely good score to secure in the JEE-Mains 2020 January session. out of the January and April session, your best score will be counted. If you feel like you can top your January score, you can go for the April attempt.
Your expected rank for January is about 3, 041. That will easily get you qualified in Advanced and should get you into most institutes that accept JEE-mains scores. Note that your overall rank might change slightly after the April session but it's totally your call on whether you want to answer it or not.