No - there is no other documentation. What you see is the "latest and greatest" information provided by RokuCo. I tried quickly on fw3 and seems that (at least) the following methods are not available there:
AddButtonSeparator() as Boolean
AddStaticText(text as String) as Void
UpdateText(text as String) as Void
AddLeftButton(id as Integer, title as String) as Boolean
AddLeftRatingButton(id as Integer, userRating as Integer, aggregateRating as Integer, tip as String) as Boolean
Someone Roku* should research and update that page with the proper versions. And/or arrange for the methods to be added on fw3
Unfortunately not. They seemed to stop tracking the date added when they switched to the wiki. Your best method is to test the channel on the legacy hardware, and add specific checks around any code that fails.
Side note, I wasn't even aware of the AddLeftXXXButton methods, so thanks for pointing that out!