To "falsify" only has meaning with respect to a scientific theory. When scientists create a theory, initially it is just words on paper - it has no particular meaning.

A proper scientific theory must include within it a way to tell whether it is wrong along with it's "meat" - i.e., any explanation or prediction about reality it offers. This is what is meant by "falsifiable". To be found "false" then means that the theory (or parts of it) is rubbish and needs to be thrown out (or amended to circumvent the particular falsehood, if possible). And finally, the way to tell whether it is false must stem from reality - i.e., an experiment or observation.

To be false, said experiment or observation will conflict with the explanations or predictions offered by the theory, and reality always wins out.

The term "non-falsifiable" in this context means that the theory in question does not come with some way to falsify it. This means that the theory can be abandonened right away without much ado - it is scientifically worthless except maybe as idle speculation or science-fiction entertainment (or to be very generous, as food-for-thought or inspirations for future theories).

To address some of your words:

Are some emergent properties non-falsifiable

The term "falsifiable" in this context only makes sense for scientific theories. Properties are not theories.

"Emergent properties" - emergence means structures or behavior appearing in a complex system as a whole without immediately being attributable to any single part of the system, i.e., the emergent property is a "new category" which has no equivalence in any part of the system. Their concrete behavior may be hard or impossible to explain or predict (see an extremely simple example: bifurcation), but if it happens, it is still part of reality and not better or worse (or more "magical") than any other part.

whether there can be silicon-based lifeform on other planets by just looking at the laws of physics and chemistry alone

There could very well be a proper scientific theory which rules out the existence of silicon-based lifeforms in the universe based only on our arbitrary definition of "life" and the physical properties of silicon. Its falsifiability stems inherently from the fact that even a single observation of silicon-based life would make it false. While at the moment we are hardly capable of making such an observation (our telescopes and space-ships are not there yet), eventually we might, and if silicon-based lifeforms exist then it is just a question of probability or time until we'd find one, if we evolve to a galactic species.

Obversely, there can never be a scientific theory which says "there can be a silicon life-form somewhere in the universe" simply because it would not be falsifiable. We can not check the whole universe for said lifeforms to make sure we don't find any, and even if we could, that would still not prove that none will appear in the future. Note that there is no philosophical content here - it is simply the practical impossibility that takes it from a scientific theory down to irrelevance.

To "falsify" only has meaning with respect to a scientific theory. When scientists create a theory, initially it is just words on paper - it has no particular meaning.

A proper scientific theory must include within it a way to tell whether it is wrong along with it's main content - i.e., any explanation or prediction about reality it offers. This is what is meant by "falsifiable". To be found "false" then means that the theory (or parts of it) is rubbish and needs to be thrown out (or amended to circumvent the particular falsehood, if possible). And finally, the way to tell whether it is false must stem from reality - i.e., an experiment or observation.

To be false, said experiment or observation will conflict with the explanations or predictions offered by the theory, and reality always wins.

The term "non-falsifiable" in this context means that the theory in question does not come with some way to falsify it. This means that the theory can be abandoned right away without much ado - it is scientifically worthless except maybe as idle speculation or science-fiction entertainment (or to be very generous, as food-for-thought or inspirations for future theories).

To address some of your words:

Are some emergent properties non-falsifiable

The term "falsifiable" in this context only makes sense for scientific theories. Properties are not theories.

"Emergent properties" - emergence means structures or behavior appearing in a complex system as a whole without immediately being attributable to any single part of the system, i.e., the emergent property is a new category which has no equivalence in any part of the system. Their concrete behavior may be hard or impossible to explain or predict (see an extremely simple example: bifurcation), but if it happens, it is still part of reality and not better or worse than any other part.

whether there can be silicon-based lifeform on other planets by just looking at the laws of physics and chemistry alone

There could very well be a proper scientific theory which rules out the existence of silicon-based lifeforms in the universe based only on our arbitrary definition of "life" and the physical properties of silicon. Its falsifiability stems inherently from the fact that even a single observation of silicon-based life would make it false. While at the moment we are hardly capable of making such an observation (our telescopes and space-ships are not there yet), eventually we might, and if silicon-based lifeforms exist then it is just a question of probability or time until we'd find one, if we evolve to a galactic species.

Obversely, there can never be a scientific theory which says "there can be a silicon life-form somewhere in the universe" simply because it would not be falsifiable. We can not check the whole universe for said lifeforms to make sure we don't find any, and even if we could, that would still not prove that none will appear in the future. Note that there is no philosophical content here - it is simply the practical impossibility of falsifying it that takes it from a scientific theory down to irrelevance.