Arrange the events in the chronological order on how Amar Dasji became the third Guru:
1) Served Guru Angad Dev Ji and the Sangat
2) Heard Guru Nanak Dev Ji's bani
3) Travelled to Khadoor Sahib and met Guru Angad Dev Ji
4) Impressed by his dedication and humility, Guru Angad Dev Ji made him the successor