Yes, that is what the evidence shows. There are multiple lines of evidence that indicate that spacetime itself was inflating rapidly for the first fraction of a second of the early universe.
And our current understanding of physics says that inflation must have been going on long before our universe began, and must have extended far beyond our universe. In fact, once that inflation began, physicists say it likely would continue forever and be constantly increasing exponentially.
I am not a physicist. But I linked to a documentary where leading physicists say this. I link to it again at the bottom of this post.
Correct. We don't know.
But "I don't know" is not the same as "I don't have a clue" or "I will never know". Again, see the video I linked to.
Those aren't my words, but yes, of course, science is continually being updated as we make new discoveries.
How many times have I said on this thread, "I don't know" regarding the ultimate reason for existence? Many, many times. How many more times do you want me to say, "I don't know"?
If you think I have made a statement that is "so adamant about [my] understanding" of this, please echo back that statement. If I agree that statement was too strongly worded, I will correct it to reflect my agnosticism.