Hey Vishwa

There is no compulsion of attempting both NDA (I) and NDA (II). It depends solely on the candidate, if he want to improve his performance in the examination then he can attempt NDA (II) as well.

NDA (I) is scheduled for 6 September by the officials and there are no updates for NDA (II) for that keep checking the official website, and chances are less of both happening on the day. https://competition.careers360.com/exams/nda