Yes,You are eligible to appear for NID Entrance examination.
If you have enrolled for NATA course,your mock test papers can be accessed with your account from edge.dqlabs.in
please check here. only one application form. https://www.dtemaharashtra.gov.in/marchcet2018/
Yes it is mandatory to fill in the CET application form, however one need not take the CET exam for NATA. Filling of application form is required for getting the unique registration number for Architecture CET counselling.