The origin of Wolverine's claws in the comics is tied to his mutant genetics. It's an inherent ability that manifests when he wants to use them for protection or combat.
Wolverine's claws can come back due to a combination of factors like his mutant abilities reaching a new peak or a scientific experiment gone right. Different comics offer different explanations for this.
Wolverine's claws come back in the comics because of his inherent mutant physiology. His healing factor works to repair and regrow them. Sometimes, specific story arcs introduce elements that facilitate or accelerate this process.
Feral cats can indeed get mange. Mange is a common skin condition that can affect many animals, including those living in the wild. Poor hygiene, exposure to parasites, and weakened immune systems can all contribute to feral cats getting mange.
Well, it happened through a complex series of events and encounters. Sometimes it was due to advanced technology or a special intervention by other characters.
Another possibility is that he was cursed by a powerful dark wizard. The dark wizard, with a vendetta against Harry, used a unique and cruel curse that transformed his hands into having metal claws. This would not only be a physical change but also a psychological one for Harry, as he would have to adapt to this new and rather menacing form, and also deal with the fear and suspicion of others who might see him as more of a monster than a hero.