I am not a native English speaker and I thought that it was not correct to say "what is IN between A and B" but only "what is between A and B". On the other hand, according to my knowledge, we could say for instance: "There were two houses with a narrow path IN between." Please correct me if I am wrong.
Because here you are asking about the subject (the thing you are asking about is the thing which is doing the "being somewhere").
In Mit csinálsz?, you are asking about the object -- the subject (the person doing the "doing") is "you", and mit is the object, the thing being done, so it takes the accusative ending -t.
Since the equivalent of "van" in english is "there is", why is it reported as wrong to translate the sentence as "what is there between the apple and the lamp?
I mean, "what is between the apple and the lamp?" sounds a bit weird to me, like if I would be asking what is the meaning of "between the apple and the lamp".
Or maybe I am wrong with the english?
On this one, I totally support the usage of the singular verb, but maybe we should mention that the plural usage is also spreading on a list of singular subjects.
To be clear, "Mi(k) között van az alma és a lámpa?" - should be singular, period.
But in this case:
"Az óvónő és a katona repül",
"Az óvónő és a katona repülnek"
is also acceptable at least.
So, I am talking specifically about a group of singular subjects followed by a verb.
I do not like this, but the plural usage is spreading. Maybe it was always in use. I don't know. (I remember an old joke from my childhood with a plural verb.... never mind.) But it is becoming widespread. Maybe it is the influence of the English language. Many many more people study English these days than a couple of decades ago. And some rules of languages can "jump hosts". I see a lot of it happening to English, as well.
Back to Hungarian.
At least in descriptive linguistics, they make a distinction between matching the subject and the verb by format/syntax and by meaning (semantics?). In Hungarian this is called "alaki és értelmi egyeztetés".
For a group of singular subjects, the verb is usually singular but it can occasionally be plural, as well.
It would take another essay to describe this, but this topic can be looked up in many grammar books.
Yes, they are correct. This is not much different from when you use a numeral with a noun.
- "Két madár ül a fán." ("Two birds are sitting in the tree.")
- "A veréb és a varjú ül a fán." ("The sparrow and the crow are sitting in the tree.")
But as soon there's at least one plural noun, the verb has to be plural as well.
Edit: but if a numeral acts as a subject instead of simply modifying a noun, the verb is plural:
- "Hárman mentek el a moziba."
- "János és Pál mindketten férfiak."
- "Az óvónő, a katona és az orvos valamennyien repülnek." (yes, "valamennyi" here means all, and not some of them. It was a surprise to me as a child, and I still can't imagine how that's possible.)