A is of a different kind than B and C. B and C are unverifiable by nature but A is potentially nonsense pure and simple. Is it relevant to your question?

I would suggest leaving out most of the question and just asking about the criteria for existence. It's a vital question. Folks bandy the word 'existence' around like the word 'God' but can rarely say what they mean. I'd be interested to see the range of answers. Your answer seems inadequate to me since our senses are limited. Also, it can be (and regularly is) argued that everything that effects our senses does not really exist. It all depends what we mean by ;exist'. . .

@PeterJ, Thanks, I edited.

Your trial fails on existence of solution for equation x+1=1. Or not, depending on what you mean by senses. If you refer to feelings and common sense as well, then it does not fail.

@rus9384, is there any ontological definition for existence that would cover both physical and mathematical objects? I guess we always need to have an additional definition for the mathematical concept.

I think yes. Mathematics is abstract and physics is abstract too. Mathematics defines existence in proposition/axiom (a few propositions) as satisfiability for some proposition[s altogether].

"If the moon doesn't exist when no one looks at it, does it exist when a mouse looks at it?" - Einstein

If something exists, it is affected by gravity.

@dtech, then doesn't vacuum exist?

@rus9384 you presume that vacuum is not affected by gravity? It is empty space, there is nothing in it, but I'd say that it does exist, and that it is affected by gravity. It is the medium in which gravity, EM radiation and physical matter propagate through.

@dtech, and how vacuum itself is changed by gravity? The things which can get into it are changed by gravity, but how vacuum itself is? You can't even verify if gravity (field) is a part of it. If you try to by placing object inside it, it's not vacuum anymore.

@rus9384 gravity doesn't change anything, at least not directly. Gravity attracts everything to everything. Vacuum attracts and is attracted by everything, it even has the tendency to clump, resulting in what mainstream physics refers to as blobs of "dark matter", which is just "denser" empty space. And since mainstream physics doesn't acknowledge empty space to be a thing, this results in other other big gap of missing stuff, which is the gravitational effect of empty space on everything, which it calls "dark energy". And those are only "dark" because the mainstream is in the dark about it.

@dtech, this is not even widely accepted explanation of dark matter and dark energy. Have you defined it by yourself? What if they just are another kind of particles? Anyway, I might assume not only vacuum but space itself as something existent. And if you can define gravity outside of space, your criterion of existence may be meaningful. But if you can't then "everything that belongs to space" makes even more meaning.

@rus9384 when was there ever a theory on the subject that was widely accepted and didn't turn out to be wrong? What is mainstream in a clearly self-destructive world is of little interest to me. Yes it is my theory. But it is based on Aether, which was prominent in the fields of philosophy and physics for over 2000 years, and advocated by some of the most prominent and contributing (albeit not promoted into popularity) minds of history , up until recently, when Einstein derailed physics from that thread into the standard model, now proven incoherent with quantum mechanics.

Existence is perception. No perception, no existence.