Upgrades are usually to a higher category of the same type. There is no charge for this
An upsell moves you to a higher type cabin. There is a cost for these.
In the past, if your cruise started in NYC, then they used Brooklyn (aka Red Hook).
If NYC was a port of call in the middle of a cruise, the it called on Manhattan.
My wife is highly lactose intolerant. The first evening, we are asked for the head waiter when we are seated. Each night he brings over the next night's menu and works with my wife to plan her dinner order. Do not be afraid to request things you like that are not on the menu.
You can follow the above for any of the buffets.
Note that to get the referral OBC, the referral must be submitted before the new passenger books.
Also, the name on the booking must be identical to the name on the referral.