The term "infinite" in itself is a theory, so yes.
Infinite is used as a variable in situations where we can't measure something because it's too big to see its limits. Information on the internet is still growing every second, so far we don't see any limits, so the term infinite is still appropriate for the internet.
Theoretically, that's an infinite list.
No, because there are a theoretically infinite number of them.
That's a theoretically infinite list. I can't write down an infinite list.
Assuming you have infinite bandwidth and storage space, that all sites and files are publicly accessible, and that they will all remain up indefinitely, yes.
Theoretically, there are infinite parallel universes in the multiverse, however it is not necessarily widely accepted that the multiverse exists.
There are at least theoretically an infinite number of possible zinc compounds.
There is no cheat that gives the player infinite life, or invulnerability. However, by typing "gesundheit" into the game while playing, the player receives full health (100 hp) instantly. By repeating this step each time the player is hurt, it is theoretically possible to survive infinitely long.
Theoretically, if we are concerning decimal numbers, a decimal number can have an infinite number of decimal factors.
You can have a tangent line for every point on a circle, so the answer is theoretically infinite.
Theoretically, an infinite distance. No one has found a limit so far.
Prime numbers have exactly two numbers. There is theoretically an infinite number of them.
Resistors limit current. In an ideal circuit (theoretically impossible) the prevent current from becoming infinite.