The father hitting the children was a turning point and major event in the story because it lead to the next scene...
Viji and Rukku running away is an important scene because that is the place where if they didn't have it, the story would have been really different.
(It's a train terminal because I ouldn't find a bus terminal)Rukku throwing her doll at the bus driver is an important scene because Rukku defended Viji which was the opposite of what happened most of the story and this was the first challenge they faced after running away.
(This was the closest I could get to a rumbling bridge)Meeting the boys on the bridge is a very important scene because this is the starting of the whole story.