Lunch is available in Kaiseki, just sushi though, dinner is more extensive.
Hot Rocks you need a reservation, Atlantide and Indochine you can walk in.
on sea days they are guest lecturers and other activities. You may be able to find out who the lecturer is from Silvesea. Evening show is usually 9:45 or 10:00 aand the night before disembarkation it is around 6:00. Again, you may be able to find out who the cruise director is through Silversea. I was on Silversea in April and masks were not mandatory except the show lounge and on excursions, even then some people did not wear them properly. Masks were recommend except for bars, restaurants and outdoors. Caviar is availble anytime you want it.
One tip is make use of your butler, he will make/cancel dinner reservations, you can have a standing order to bring coffee first thing in the morning, set up canapes in your room prior to getting ready for dinner or pre drinks in the bar, ask for fruit bowl in your room, polish shoes, if you like having a drink in your room he can stock your bar fridge with preferences like champagne or wine, also a bottle,or hard liquor if you like also.
You will absolutely love cruising with Silversea, from the food, friendly staff and wonderful people you meet on board. Enjoy!