Do visa authorities ask questions when we go to lodge application for student visa. I hear that they also conduct telephonic interview?

Actually I passed my 12th in 2008 and was doing CA but could not make any headway. Now I have taken admission in a NZ college, will the gap of 4 years go against me. Secondly my father's sister has sponsored me but her bank statements show overdrafts (she has a business), will it be accepted?