why one can not file a complaint without giving full particulars may it be a tool against antisocials?

Answer 1

You can file a complaint, without revealing your particulars. If it is going to help them in their investigations and if they think that information provided are helpful, they can offer a reward as well.

Answer 2

You have to give some details when you file a complaint or else they won't understand what exactly happened. Now if you are referring to your personal information, sometimes you can request that be kept private.