Nice to see you again Roger. We’ve been over this already… multiple times: see here, here, here, or here.
The reason the Big Bang is a successful scientific theory is that it can describe mathematically how the universe evolved after it began. We can experimentally test up to approximately 10 billion electron volts at the Large Hadron Collider which would tell us what the Physics of the universe would have been like about 0.000000000000001 seconds after it ‘began.’ We understand very well the Physics of what particles would have existed and how they would have formed. We understand the formation of the first nuclei (as predicted by Big Bang Nucleosynthesis) which actually describes the distribution of elements that we measure nearly 14 billion years later. We predicted the Cosmic Microwave Background (based on atomic physics and black body radiators) and then later measured it. Everything about the Big Bang Theory has been quite remarkable…
BUT, we cannot experimentally measure any energies before 10^-15 seconds after the unvierse ‘began.’ As in… they are in the category of theoretical physics and in many cases, remain in the realm of untestable hypothesis. Certainly quantum mechanics would have been important in this regime… but so would general relativity… but the two don’t talk to each other! Hence the previous video I shared on Quantum Gravity and the fact that nobody knows how to successfully unite the two yet tells me you are blowing smoke at me again.
In summary: We do not know in the scientific sense what happened before this point. Many cosmologists are actively trying to solve such problems. Yes, Stephen Hawking was one of them and there are many others. But just because we do not know what happened before a certain point doesn’t mean that the Big Bang Theory is in any way invalidated.