Every, like each, is always used with a singular
noun form and therefore with a singular verb form in
English because we are counting the things or people that we are
talking about separately one by one:
- Every child in the class plays a musical instrument.
- Every instrument belonging to the school is tuned
everybody / everyone / everything
It is true that everybody and everyone refers to
everybody and everyone in a group of people and everything
refers to everything in a group of things. Even so, they
are still perceived individually or as a totality, so the singular
verb form is still maintained:
- Is everybody happy with that? Does
everyone understand my position?
- Everything she owns has been stolen.
all - with singular verb forms
All is more often used with plural verb forms, though
sometimes it is used with singular verbs. This happens when
we are referring to all as a totality of items under consideration.
Here, all is close in meaning to everything:
- Is all well with you?
- Don't cry! All that matters is that you are safe.
- That is all she has in her suitcase: a blouse,
two dresses and a pair of sandals.
- All she wants now is to get back home to her parents.
- All that happened was that she got on to the wrong
Note that in this sense, all is often used together with
a relative that-clause, all that matters, all she wants,
etc. In your example, Ihsan, as there is no relative clause following
all, we would be more likely to say:
- Is everything finished? ~ Yes, everything is finished.