Hanuman returns is a movie based on fiction rather than mythology.
The story begins with a battle between the Devs and the Danavs. In the end, the Danavs have to go to Planet Shukra (Venus) along with their guru Shukracharya. Shukracharya has a magical wand called Sarpdansha using which he can make dead danvas alive.
On the other hand it is seen that the Devs are busy in swarglok, they have become 'tech savvy' and converse in 'Hinglish'.
Hanuman sees a village boy who is bullied by local hooligans. He decides to help him but for that he has to take birth like a normal human, he shares this with Brahma and then goes for this. He is born on earth like a normal child (with a cute tail). He takes admission in school and teaches a lesson to the local hooligans, Gabbar Singh and his gang.
On planet shukra there is a fight between the danavs and accidently that sarpdansh comes to earth. Now danavs also come down to earth to search for it and they have to face Hanuman.
What happens next? See 'Hanuman Returns' to find out.