The difference is the app you can pick the steps individually, specifically picking an arrival time without filling out the rest. The website you have to do everything else first before it lets you pick a time.
Reviews are inherently skewed negative. When I read Reviews for any tourism related service, it's usually pretty easy to filter out the unreliable reviews
With some of the more popular tour providers, there's a good chance there will be people on the bus with you that are going on the RC-sponsored version of that tour.
Early 2025 would be about the 5 year window for her next drydock. Maybe dock slots were limited and this was the best window available to get it done before the summer season
The RC website can do weird things with time zones (like how the app and the website show different dates for your cruise check in date). That's what I assume it is.