Our waitress discouraged that, she said it would take a long time for the kitchen to add in the items. However, no problem to arrange your own tasting menu up front and they will walk you through the choices and make suggestions.
The dining guide I posted only covers dinner service. I remember them being open for lunch, but we didn't go and do not have a menu from the lunch service. I believe the sushi menu is the same every night except formal night when they do a set menu. I didn't see any meat (I'm assuming you mean from land animals) items on the menu, but I would imagine the menu changes periodically.
Our hidden gem is Sweetfield Manor. Only 10 rooms, each one is unique. Not as posh as a luxury cruise, but something different and the basics (bed, AC, etc.) were very good.
That could be, in our case we found the dressing too lemony and that is an ingredient that they mix in. However, I think the main culprit is the "anchovy emulsion" which is pre-made.