Hors d'oeuvre as no abbreviation in French. The term can be replaced by 'entrée'.
Approximately "or derv".
There is no difference in "appetizers" and "starter courses", as starter courses simply refer to the food served "at the start of a meal"--just like an appetizer. It's typically more of a...
hors d' oeuvres that are hot... or appetizers that are hot