Breakfast is available in all the MDRs, the buffet and the Quays, you can use the virtual queue for the MDRs but you can also just turn up.
The app, which is really a web page, is only available once on board, entertainment in the theatre and Limelight club, as well as the speciality restaurants and chefs table,, can be pre booked on the website, but the MDRs can only be booked once on board, or daily by joining the virtual queue, which is the major choice.
On celebration nights formal dress will be required in all the MDRs, epicurean and Sindhu, the chefs table and the crowd nest and emerald bar. The chefs table is held in a private area of the buffet, you no longer meet the Captain and for the MDRs you join the virtual queues as normal.