However, I'm not sure the name of the betting service, neither if it was the first casino to come online or not. Maybe someone more acknowledged on this matter than me who also reminds this can answer with more accuracy.
I remember the platform as I played there a number of times but like you, I'm not sure about the name. Directbet.eu or something similar is the name. I liked the fact that you didn't need any account registration or KYC or any of that. You just place your bet and get it back if the bet was won. Great concept but right now, something like that won't work because the regulatory restrictions for such platforms is now high as well as transaction costs is almost 5-10x the amount it was back then. Still, it was a fun concept; one that I liked.