If I have not answered all questions in NTSE (Stage 1) will I be disqualified?
In ntse stage 1 there is a particular cutoff set by the organization.
If you clear that minimum cutoff then you will be given a chance to the interview round.
And in good there is no such rule that you have to attempt all the questions. Do only those questions which you know. And it has also negative marking so beware of that too.
Try to give your best and correct responses to the questions. And it is not necessary to attempt all the questions. Even if you leave the questions that your don't know you will not ne disqualified.