in a episode of pkmn a riolu has aura sphere is that possible to obtained?
In Legends: Arceus, Riolu learns Aura Sphere at Level 21.
In Pokemon Ranger: Shadows of Almia, the mission "Rescue Kidnapped Riolu!" allows players to transfer a Riolu with Aura Sphere to Generation IV games. Though Nintendo has stopped supporting the wi-fi required to access this mission, it can still be obtained via the DNS Exploit.
Aura Sphere (Bulbapedia)
No , a normal Riolu can't learn Aura Shpere.And In the Anime all things can happen.In this case Riolu knows Aura Shere beacuse, according to the anime, it belongs to a Special Kingdom