Freehks.com is not a single game, but rather a platform that claims to provide "unlimited gems" and premium currency hacks for a variety of popular mobile games Platform Overview
: This is the bread and butter of the site. You’ll find offers for everything from casual puzzles like Tropical Crush to strategy epics. Freehks.com Game
If you are looking for games that offer real-world rewards, these platforms are currently popular: Freehks
It's also possible Freehks.com once hosted or linked to a simple Flash or browser-based game (e.g., a puzzle, quiz, or dating sim themed around Harry Potter characters). The write-up you found might be a nostalgic retrospective on that game. Freehks.com is not a single game