On the former, you should bear in mind that pure causal loops, due to this problem among others, aren’t strictly speaking forbidden by physical law. They just have such severe constraints on them as to make them very very very very very very very improbable, which ought to amount to the same thing. (The same goes for impure causal loops, but knock off one very.)
Their protocol exists because within delta of impossible isn’t impossible, and as we all know from Pratchett, million-to-one chances happen nine times out of ten. Especially in a universe that has extant examples of probability-mangling technology.
On the latter, there’s a more detailed explanation of this over in the Timeo Eldraeos word-of-god thread (read the spoilered bit about how Worldline Demux works):
But here’s a short relevant excerpt:
The way universes naturally work (and this is a horrible, gross, lies-to-children popsci version of the theory) is that in macroscopic quantum systems, like universes, you can approximate the probability curve of aggregate wave function distributions as something like a bell curve. The resolved classical universe as we actually perceive and experience it is essentially the peak of the curve. The falloff to either side, for the most part, can be conceived of as naught but shadows and echoes.
They aren’t “real” alternate universes, but those shadows and echoes can, in theory, be manipulated. Including by cloning neverweres into the real, classical universe.
(No-one has turned this into practice, yet, but occasionally strange artifacts turn up whose best explanation is that they didn’t come from the “real” worldline.
Think of this process as something like pair production, where sufficient energy can stress the virtual particles apart and leave you with real particles. Except you’re doing it (a) with macroscopic objects, and (b) at right-angles to reality.)