Hey furqan.

That depends. If you get a good rank in the current exam and want an even better rank then take the jee advanced exams on April. As the NTA will take the best out of the two.

Hey Furqan

No it is not necessary to give April exam.

But it will be a chance to improve your january score so i would suggest to give April exam.

Because even if you score less than January your highest ( January ) marks will be considered for final merit / rank list.

So good luck