My two cents on a couple of these:
“Was there anything before the big bang?”—A poorly phrased question, since time is postulated to be a consequence of the big bang. There is no “before”. Better to ask what grander or more fundamental thing is the universe, including the big bang, a part of or derivative from.
“Will the big bang become an untestable theory?”
Not sure how you prove the past, so it in a sense is already an untestable theory. You could test a theory that’s consistent with discovered physical evidence of a big bang, though.
Only one problem: the universe is expanding at an accelerated rate, which is inconsistent with the Big Bang Theory. As with any explosion, the rate of acceleration of mass is at a maximum immediately following the “bang,” and then naturally slows down. A Nobel Prize, however, was awarded to scientists who discovered that, in the case of the universe, just the opposite is true - it continues to expand at an accelerated rate, supposedly billions of years after the alleged event took place. Thus, the Big Bang Theory falls completely apart.
And who was there to observe the fundamental particles that made up the mass responsible for the Big Bang if no intelligence was there to observe and thus collapse the probability wave functions of those particles to a particular eigenstate? Unless, of course, that “observer” was the Almighty Creator. One must then assume that most modern-day quantum/astro physicists are devoutly religious, yet most I run into are either atheists or agnostics. What’s up with that?
“A poorly phrased question, since time is postulated to be a consequence of the big bang. There is no “before”.”
If time didn’t start until after the big bang, then the big bang could never have happened. Without time, no change could occur, so whatever pre-existed the big bang would just continue to exist unchanged.