Hello Neha,

First of all, you need to choose an optional subject out of the list of subjects like History, Geography, Political Science, Economics, General Science, Sociology, etcetera as per your interest. Since you want a subject related to Architechture, you can choose accordingly.

Coming to category, I think you are talking about post and designation of an IAS Officer. It is decided on the basis of merit in the UPSC examination.

Hope this helps