With RCI there's usually three outcomes to any issue: the policy outcome, what most people encounter and the exception - I'll let you figure which one of those you experienced.
The app works the same across the fleet and wifi coverage on most ships in common areas is pretty good. As long as you have a wifi connection, the app works the same, regardless of ship. Sometimes, the issue is the setup on the individual phone, not the app.
It was on the GGG flier for at least two weeks and the price now just went back up to kinda what it was before it went on the flier. The ZI GTY rate I see is $577pp base fare, which is still pretty good (less than $50pppd rate on a newish O class is great) - you can book this via a dummy second person. About 60 days out is kinda where most of the deals happen - by the time you get to about 30 days out, RCI tries to get the ship fairly full and prices go back up.
I should have said it may also depend on who you get at RCI as they or may not reprice it - dropping a person should be safer from repricing. @Ourusualbeach may have better info.
The wiki portion of cruisedeckplans or other cruise related site will list the date of the previous dry dock - add 5 years to that if the ship is less than 20 years old. If older add about 2.5 years.
Very unlikely, more like RCI wants to confuse consumers by recategorizing cabins all the time (without any actual changes on the ship). Even the ship may not know exactly what is affected till the work starts.