Грамматически подходит только вот это:
As well as in Britain you should greet a person when you first meet him/her during the day.
But you shouldn't say "Good appetite" to people who are having a meal.
When in Russia don't forget to give uneven number of flowers for a present.
Но я первый раз слышу совет не говорить "Приятного аппетита" людям, садящимся за еду.