If there is a great power capable of producing all things within its own mind, and if this is indeed the nature of the universe, then this would be the only reality in existence. The world would be mind stuff, this would of necessity include humans. However, it seems that this great power would have to impose laws on such a creation, natural laws we might call them.
Human minds would be individual minds within the great universal mind. Controlled by the laws, all humans would seemingly be guided into a general recognition of things in the way the great power required. Thus, if it was required that all humans should recognise, or believe in, a material existence, then so be it. Each human would recognise other humans, and would come to understand what was meant by life and independence, we would all exist within this reality. As we would all be products of this super power, then such a power could impose anything it chose on the world, including free will for humans: or, if it wished to keep control then our lives would be determined.
Alternatively, if this super power was capable of producing actual matter. then it might create a material world; everything, including humans, would be real in the solid sense, real material objects. It seems that this is the way you are using the term real in your question. The implication being that things can only be real if they are out there in the world as solid objects. As we have considered another way in which things can be real as mind stuff the fallacy in your question is revealed. You are using a pre-conceived idea of reality derived from what philosophers call a naive view of the world.
This view is to some extent held by materialist philosophers and probably most scientists. But there are some philosophers called idealists who take the view that reality is mind stuff controlled by abstract laws. In fact some philosophers, both materialist and idealist consider the abstract laws of mathematics, space and time, etc. to be more real than what are called material and mind stuff objects. Some of these are called rationalists, who believe that things can be discovered about the real world, not only by direct perception, but by rationalising, cogitating (thinking) about things.
Your second question by implication hints at solipsism, the view that only oneself exists. Although a seemingly absurd proposition, it is still debated by philosophers. I wonder if it is a comfort to the solipsist to believe that he/she cannot really die, they just stop imagining, and it is the world that actually dies?!