You are suggesting possible future events that would provide evidence for a multiverse. That does not make something a falsifiable theory.
Analogy: it could happen that tomorrow Jesus Christ descends from the heavens and brings the day of reckoning. That would prove Christianity to be true, but the fact that this could happen does not make Christianity a falsifiable theory.
A falsifiable theory is a theory that predicts something that we can (in theory) measure today (possibly requiring infinite resources etc).
Your second example (which is not a multiverse theory at all) is actually a good example of a falsifiable theory. People have calculated [1] that if spacetime was folded back onto itself at even just a single point, it would leave a distinct signature in the cosmic microwave background. We do not observe this signature, so we are pretty sure spacetime does not fold back onto itself.
Ok. What if spacetime folds back onto itself over a very long distance? Wouldn't that be (viewed locally, with our limited instruments) as if another version of spacetime touches upon our version of spacetime?
Physics will always be based on observations. Consciousness is fundamentally hinged TO observation. I'd argue that the way your brain works is more fundamental to reality than the physics causing a Mhz of conduction throughout your synapses. In summary, all bullshit theories are possible in spirit of deceit. For why should good senses be wasted on a cohesive system when the mind is simply a slave to its own devices?
Or if spacetime folds back onto itself?