Tyke,
I thought that I was answering the question for RB24 as well as the receivers but as you state that may well not be the case.
As you can see from the attached shot RB24 shows the hex code, registration, full aircraft type, Type ICAO code, airline in fact all the details you mention apart from the msn. I haven't delved far into RB24 as I use the receiver for monitoring traffic but I will ask if the full aircraft details are available somewhere on RB24 and make the suggestion to them that its inclusion would be appropriate.
I see that information, but only from clicking LIVE planes on the map. None of that data (except the generic typo) shows via the specific aircraft data link :
https://www.radarbox24.com/data/registration/C-GWAZRegarding YR-BGJ the page you gave the link to looks like flight history so as the aircraft has not been picked up in its new guise, there are no details to show and expanding the page as detailed above would be required to show the info on the aircraft itself as well as its flight history.
OK. I guess that confirms there's no way of checking if you already have a particular entry then, if it's not been picked up somewhere since.
Regarding the Boeing flights I have tended in the past to use the Puget Blog for their first flight details but as you are aware it has become rather haphazard in being updated so any information you are able to provide would be appreciated. If its on the Puget Blog its in the d/b and I receive the weekly FAA list updates as well to update the database so am relatively up to date and the new ICAO type codes were added the day they were published.
"Haphazard" is certainly one word to describe it :D although I have several words of my own that are probably best not repeated here.. In short, you should take what's written on there with a large pinch of salt, particularly the hex codes. A growing number of them are complete fabrications.