I’m a simple person and really can’t understand quantum theory.
The question is whether this description of something from nothing in a subatomic particle (not that I understand what a subatomic particle is either—even Wikipedia couldn’t explain it to me) is correct in any way or form, or really not at all?

And also, is it in several places at the same time—for example like Elijah the Prophet, who drinks at about the same time a little bit from all the cups of “Pour Out Your Wrath” in all Jewish homes? Or really not? Or for example is that just unrelated to the discussion, like how 1+1 = 2 at the same time everywhere in the world at all times, and that doesn’t really create a contradiction?
Is there some kind of clue that a layman like me could use to receive the two answers about the subatomic particle? (And roughly understand the general direction.)

Maybe you mean the creation of particles from the vacuum. That is one certain description, but it’s not clear that this is really something from nothing (maybe there is something there that physics does not describe).
As I wrote, a particle in its classical sense (a little ball of matter) cannot be in two places.

In the vacuum there is quantum energy from which the particle is created. This is a quantum vacuum, not a vacuum in the sense of “nothing,” as the term is used in modern language.

As for what you mentioned about Elijah the Prophet drinking a little from every cup—if that happens simultaneously, wouldn’t it come out that he drinks a halakhically significant quantity, and then he would be obligated in a blessing, and then in effect he would have decided that a fifth cup is required, and then all of us would be obligated in 5 cups on the Seder night?!

Seems to me that after he drinks from all the Jews, even if only a little,
he has the status of someone drunk, who is forbidden to issue Jewish law rulings,
and then the doubt remains.

You’re right, he’s even mixing several kinds.

But from his actions themselves one can learn in practice what should be done.