There are questions which are difficult to answer. Inquiring mind trying to be consistent answers them according to its own culture, not science. The very concept of knowledge fails in such areas of cognition.
Question 1. What is the ultimate cause of everything? What is the creator of the Universe? If the beginning of the universe had a creator then who is the creator of the creator? If the creator made himself, what is the reason of such creation?
Question 2. Is there any mind in the Universe different from ours? Another mind may be different so much that interaction with it may be impossible or virtually impossible.
Question 3. Is the Universe controlled by determinism? Quantum physics tells us that quantum processes are fundamentally non deterministic for any observer. So the question is, is it non-deterministic for the Universe itself as well?
Question 4. Is there free will in a deterministic world? Assuming, that the quantum world is not needed for explanation of intelligence and consciousness, how certain laws create your own personal free will?
Question 5. How the past can be multiple? The double-slit experiment proves multiple histories ....