I thought the identity of the Queen's voice actress was lost to history so I don't know where Verna Felton came from

. Her name too was a mystery, but apparently someone from the Studio said it was always meant to be "Leah".
Prince Ferdinand - The Disney Wiki states:
At the 1938 Oscars, Shirley Temple mentions the name "Ferdinand" among others while presenting Walt Disney his awards. Many have interpreted that she was referring to the Prince, saying that Ferdinand is his name. However, she was not referring to the Prince, but rather to Ferdinand the Bull. As confirmed by Dave Smith, Historian of the Walt Disney Studio Archives, the Prince was never given a name in the film and "Ferdinand" has never been used as one by the company. Despite this, many Disney fans still believe that the Prince's name is Ferdinand.
Disney Latino revealed through a video of Top 10 Romantic Moments the name of the prince is "Fernando" Spanish translation of the name Ferdinand.
Disney France once revealed in a TV-spot that his real name is Florian. That same TV-spot also revealed that Prince Charming's real name is Henry (or "Henri," as it would be in French).
The name "Florian" was allegedly used by Disney when they started the Disney Princess franchise.
There's a story that there are artwork and documents in the Walt Disney Studio Archives that call the Prince "Frederick".
Queen Grimhilde - again, the Disney Wiki states that her name "was given as Queen Grimhilde in some old publicity material and comics, but the Walt Disney company does not seem to acknowledge it as canon anymore." IIRC,
Fairest of All: A Tale of the Wicked Queen prequel book doesn't mention her name either.
Prince Adam:
It is stated in products licensed by Disney (such as the 1998 video game The D Show which was developed by Cyberflix) that Adam is the Prince's name. However, it is not his name, as it has been stated in the directors' commentary included in the Beauty and the Beast DVDs and Blu-ray as well as the Disney.com FAQ and D23.com that the character has never had an actual name; he is only referred to as "The Beast" or "the Prince". It was mentioned the writers and producers were so busy that they forgot to give him a name. In an interview with Glen Keane, Keane admitted that the Beast never had an alternative name prior to the film's events.
Regardless, the name Adam is still used, occasionally, in the Disney Prince/Disney Princess merchandise as the name has gone completely viral.
However, it's possible that some animators and crew members did refer to The Prince as 'Adam' during production, as Paige O'Hara, the voice actress to Belle, recently confirmed it during a fan Q&A while adding "Disney will always deny it." However, it's unknown if the name given to the character during production on the original film or during production on one of the film's sequel projects.
So basically, none of them are truly official.