For version 1.5.9 specifically, the activation process connects to Forward Development’s servers. The developer has deprecated older key validation servers for some legacy versions, meaning even legitimate old keys may fail to activate if the server handshake protocol has changed. This makes finding a "working" free key for this specific version even less likely, as the server will reject unauthorized codes immediately.
If you're interested in installing City Car Driving, I recommend purchasing a legitimate activation key from the game's official website or authorized retailers. This will ensure a smooth installation process and provide you with a fully functional game. city car driving 159 activation key free install