Most claims of extreme ranges are bollocks aimed at punters who don't know how to check (hence the nonsense about Mariah Carey, who is a rather ordinary soprano). I would suspect the same about Halford unless someone provides some firm evidence.

Minnie Ripperton could do things to musical effect across the whole of her range, but it doesn't seem like she could sing intelligible words up at the top. The top end was a sort of highly controlled and accurately pitched yodel.

The Queen of the Night's aria in The Magic Flute is one of the most notoriously extreme pieces in the entire classical repertoire. Nobody sings it with really clear verbal articulation at the top of the range. It sits higher than most soprano parts, but its range is only two octaves.