Please, DO NOT BELIVE IN THE CASTE SYSTEM! The Guru's rid our religion of the caste system ages ago! Yet we have bought it back! Why?
Yes ,it is jat surname if he/she belongs to ludhiana.
No, it is the name your parents gave you at birth, for example, Joan or Sean.
yes
A full name is what people call you, and a last name is what you have for people to know what family you are from.