'what is the name of the railway stretch between east & west of australia?

Answer 1

The Indian Pacific is what you're after; it travels between the Indian Ocean in the West and the Pacific on the East Coast. (The Nullarbor is the stretch of plain beween Western Australia and central coast of South Australia; Null-Arbor = no trees. And there aren't.)

Answer 2

The Indian Pacific is the train that travels over the Nullabor.

Answer 3

the Nullabor