I always assumed the Teams should not be renamed from default names or else game may have odd behavior & freeze--so not sure renaming is possible. Team or Coaches records may be able to be edited with EA db editor but I don't know how. I know Vikesfan edits these manually in game or with the editor.
Yes, through EA DB editor or NCAA dynasty editor you can make 2 players have the same jersey# eg. a defensive and offensive player can have same # like in real life. Not sure if 3 or more players with the same # will cause any problems. I never tried that.