Yes and yes. As far as I know, he hasn't appeared in the new series (I refuse to acknowledge that as any sort of successor to the original Teen Titans animation), and Clow Reed is indeed from CCS (and is actually really surprised that Tsubasa!Sakura claims he's her biological father).
The other two are Big Bads from their respective series, Fairy Tail and Deadman Wonderland, though Hagire is unambiguously the more malevolent of the two and is a psychotic mad scientist. Zeref's a total deconstruction of the 'dark wizard' archetype, and is way, way more sympathetic of a character. Both are really great series, I highly recommend both.
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The other two are Big Bads from their respective series, Fairy Tail and Deadman Wonderland, though Hagire is unambiguously the more malevolent of the two and is a psychotic mad scientist. Zeref's a total deconstruction of the 'dark wizard' archetype, and is way, way more sympathetic of a character. Both are really great series, I highly recommend both.