Question

how did valli gather all the information about the bus​

Answer 1

Over many days and months Valli listened carefully to conversations between her neighbours and people who regularly used the bus. She also asked a few discreet questions here and there. This way she gathered all the information about the bus.

Answer 2

Valli planned meticulously before undertaking the bus ride. She would listen carefully to conversations between her neighbours and people who regularly used the bus; and she also asked a few vital questions here and there to know all the details about travelling in the bus. This way she picked up various small details about the bus journey.