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, I am capable of answering every question, given enough time and help. 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 that can be posed.
Let me show an example of a question that I do not know the full answer, but I can help you get closer to 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, that includes the reality that God could choose to be nothing, God could choose to not exist. God would exist and not exist at the same time.
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, but cannot peer 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 myself and it is what joins us together, if I can know myself fully, then I can understand my humanity, the part that I share with everyone else who is human and help others through that understanding.
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.