The laws of physics regarding gases show that when gas is compressed it heats and expands, in other words without an outside force working on the gas it will not of its own accord contract to such an extent as to form a star. That is all I am saying. If you want an explanation of the laws of physics buy a physics book. Physics has as yet been unable to explain a lot of the Big Bang theory, partly because of the laws of physics regarding gases. An interesting and short read is God and the Astronomers by Robert Jastrow, founding director of NASA's Goddard Institute for Space Studies.
You appeal to reason and logic, but refuse to discuss reasonable questions regarding evolution by stating "I don't know". Evolution is illogical when the complexity of the animal kingdom is taken into consideration. The Big Bang has so many unanswered questions it is illogical and unreasonable to teach it as fact. Stephen Hawking has come up with a cosmological explanation for the universe that does not require science. As Scorpion posted mathematicians have calculated the odds of evolution being a viable theory as mathematically impossible. So what science do you want to appeal to? Mathematics is pure logic.
After 40 years of reading science and theories the most logical explanation, at least in my mind, is: "In the beginning God created the heavens and the earth." Can I prove it using science? No. Can you disprove the existence of God by the use of science? No. So until science can prove the Big Bang and evolution I will apply reason and logic to what I read. And God makes as much reasonable logic as some unknown glob of energy exploding at some unknown point in space and at an unknown point in time that by unknown mechanisms coalesces into a complex universe that demonstrates a unique design.
As to the Nepalese, since they probably emigrated from India, Mongolia, or China the answer to your question is yes, they do have a flood myth.