Yes, except very late in the booking cycle (usually inside final payment) those lower priced offerings may be for new bookings only. In that case it may not happen.
Then a Key purchase makes even less sense. You can probably get assistance with boarding without the Key and I can't think of anywhere else it would help your situation.
No trick, when you open a browser on the device and go to the Voom login page there’s a link for both Play and App stores. Click on the appropriate one for your device and the timer starts on the free Wi-Fi. It won’t work on a laptop - only a device which would normally get the app from the store (I think the redirect to the store is what triggers the free Wi-Fi session).
Pro tip: RCI lets you have 15+ min of internet access while on the ship to download the app by clicking on the App or Play store on your device. Even if you already have the app installed, you can get internet access this way - some frugal folks can milk this to get some free access.