We were there in 2018 I think. We thought spending $450 was a lot.
RC realized, likely due to cabanas on Coco Cay, that they were woefully underpriced.
That's not what RC's permission letter says though.
https://www.royalcaribbean.com/content/dam/royal/resources/pdf/minor-traveling-without-parent-or-guardian-form.pdf
The OP is asking about a permission letter for an 18 yr old, which is not needed, despite the 18 yr old not being old enough to be the oldest on a reservation.
That just says the 18 yr old can't sail alone. It doesn't say the 18 yr old needs permission from his parents.
On the consent form RC provides, minor is 0-17 yrs old
No, just LNG.
Fuel cells are a long way off from practicality at a larger scale. Viking has them on some new ships, but will be used in limited manners (like the fjords). MSC has a couple larger ships with H fuel cells, but will only be able to use them in ports.
You're better off with bringing your own fold flat one, but when my son was younger we asked the room steward for one on a couple cruises and only once did they not find one (and the room steward apologized).
I see a cruise that puts me in a 2 BR GS for about that price, too.
People complain about rising prices, but there are legit good deals out there if you book early.