According to RCI , if you log into your account, you are able to book cruise enhancements - one of which is 'specialty restaurants' It is not open at the moment for us, but it should be for you if you are sailing in Jun.
No, you cannot book the Speciality Restaurants in advance - they will be taking bookings on the first day. Shows are on twice a day. There is an auto 15% tip added to drinks bill - no need to tip any more.
According to RCI website you can pre book restaurants up to 3 days prior to departure. It's under the 'shops, gifts & gear' section. Top left on 'home' scren. When it becomes available for our sailing we will be doing this. It's not available now for us, as we don't sail until July on the Independence.
No you cannot book restaurants yet on line. There is a roll out plan with the dates but is not available for Independence on May 17, you can book for this ship after June 11t.