I never understood why Steve Urkel who i assumed to have low self esteem because he had to make up a fake name called Stefan, if steve urkel liked and love himself like he claimed in the 9 year run wouden't he just call himself Steve instead of Stefan, why would steve feel the need to define his new outgoing personality by calling himself another name like stefan ???

Have you not seen the episodes where Steve undergoes a "The Strange Case of Dr. Jekyll and Mr. Hyde"-like transformation? I think the name Stefan was used to help differentiate between the two personalities- who eventually became separate characters altogether.

Yeah i seen it plenty of times my bad i forgot about that one lol