Hello,

No, you cannot complete the part 1 after the last date for filling the application form and payment of application fee. You will get admit card only if you complete part 1 and part 2 registeration and pay the application fee successfully. If you haven't completed the part 2 registeration then your application is rejected you will not be able to appear for NDA  entrance exam. The last date to fill the application and pay the application fee onli is January 19, 2021 that is today.