In Buddhism, does "God" exist or not? In Buddhism, is the existence of "God" accepted, or not? If not, what is the reason?
It depends on what you mean when you say "God" and "exists". In Buddhism all entities (objects) are abstractions or models, conceptual labels on top of mind-made constructs. So all things really exist in one sense, but don't really exist in another sense. God is like that too. If by God we mean "The Absolute" then it in one sense it obviously exists (since everything is included in it) but then in another sense The Absolute is just an abstraction so it doesn't really exist. It certainly exists as concept or model in our mental world.