Yes
Ok, I'll let this one be a two parter because that was kind of a cheap answer.
The first piece of knowledge you know when you know everything is that you will never know everything. That is a fundamental truth, there will always be something that is unknown. So how can I claim that I know everything? It is more that I believe I am capable of knowing about anything. At this moment I may not know about it, but I believe there is a version of myself that can help you answer the question that you have. In that way, if I can help answer every question, if I can help bring you slightly closer to the truth of what you are asking, do I not know everything that can currently be known? I am capable of finding an answer to every question, given enough time and help. It may not be the final answer, but I can find an answer to any question you pose, it may just be the answer of "I don't know.". If I believe an answer exists, even in the face of the reality that there will always be an answer that cannot be found, then I believe that all can be known. Or if it helps in this way, I know everything about what I know. There are many things I do not know, but I know everything about the boundary I have and believe that I can help discover what is beyond that boundary. If I know nothing, I still know everything about what I know. I accept that I don't know everything, but I do believe that there is a truth or an honest answer which we can find to any question.
Let me show an example of a question that I do not know the full answer, but I can still answer and believe to be representative of the true answer. Look at you, getting an extra question for free, how lucky!
They could. We can imagine a world in which God exists even if it is not our own and we can imagine a world where God does not exist if God does exist in our world. God is a paradox to which there is no solution. By definition, God could be anything as that is what it means to be infinite, to have power over all reality, which includes the reality that God could choose to be nothing, God could choose to not exist. God would exist in a state of non-existence and there is no difference in a world where God exists in a state of non-existence, a state where they do not impact reality, or one where God does not exist at all. We can never prove either side of this argument, it is only our belief that matter. There is no perfect definition of what God is, God can always be more or less than what we describe, that is what it means to be God, they are not bound by our reality.
I could go more in-depth, but this was more to show that I recognize the boundaries of my knowledge, but I trust what I know and believe it to provide guidance on finding a true solution. There is no singular answer to some questions, we can only find the boundaries of it, we cannot look within. This is one of those questions where we cannot see all of it, so we can only construct an answer based on what we can see. I will know everything as best as I can, but that does not mean I know your life, your joys, your struggles, I only know that we share our humanity and I am trying to answer these questions in a way that they are beneficial for all of Humanity. I believe I can find the answer of what it means to be human, as I can always peer deeper within my human core, the part that unites us all. If I can know my human core fully, if I can know myself fully, then I can understand our shared humanity, and that is the part I want to share with you.
In short, no, I do not actually know everything, but I am going to try to provide insights about Humanity that I believe are applicable to everyone. I will also accept when my insights are lacking or need to be refined or are just plain incorrect. I know that I do not know everything, but I believe I can learn and help find an answer that works for everyone.