I have completed my 10+2 this year. i.e.my age is 18 so I am eligible to apply for NID 2019???
Firstly candidates must have passed 12th grade from recognised University and must be minimum 20yrs age. Hence you shall not ve eligible for NId DAT exam.
Detailed eligibility criteria below for reference
https://design.careers360.com/articles/nid-dat-eligibility-criteria