The answer truly is "no one knows". Half the firearms attorneys say one thing, the other half says another. Trusted FFLs with attorneys say 1 thing, GOAL says another. Find your risk tolerance and go with what your gut tells you.
Not really. If we’re talking about whether a personally submitted FA-10 determines whether a lower was a rifle first, then that’s pretty clear. It doesn’t.
And whether an FFL can look up FA-10 submissions, the answer again is a clear no.