Are they any working Habbo retros?

Habbo retros are illegal in every way. Habbo Hotel has every right to sue Habbo retros.

All private servers are illegal, but most of them go uninterrupted by Sulake, because they pop up by the hundreds every day, and for them to be explicitly shut down, Sulake would have to go to court with all of them. However, sometimes companies just issue C&D emails to server owners, and that often closes hotels. (Cease and Decist messages, are a threat of legal action against the server)