Here is a list of seventeen questions that either qualify as pure speculation (i.e., there is no way to know) or fringe (i.e., questions that are odd and hardly ever asked). I came up with 17 of them. Please add to the list in the comments. I may start a blog series dealing with each one in the near future.
1. Had Christ not been killed, would he have died?
2. How long were Adam and Eve in Eden until they fell?
3. How did Peter recognize Elijah and Moses on the mount of transfiguration?
4. Why did God put the Tree of Good and Evil in Eden?
5. Did Adam and Eve have belly buttons?
6. What was God doing before creation?
7. Could Christ have died another way and secured redemption (e.g., stoning)?
8. Why did Christ say, “It is finished” before he died? Was his physical death not required for the atonement, or did he mean, “It is just about finished”?
9. Did Christ ever get sick?
10. Had Adam and Eve not been booted out of Eden, would they have lived forever, even after the Fall?
11. Why did God put an angel to guard the tree of life? Why not just destroy it?
12. Is there a hierarchy among demons like in the animal world, and do they experience the noetic effects of sin? Does the left hand in the demon world always know what the right hand is doing?
13. Can a believer be demon-possessed?
14. Will there be sex in heaven?
15. How did Peter recognize Elijah and Moses? (I just like that one so I put it twice)
16. How did Satan show Christ all the nations of the world from the top of a mountain? (Luke 4:5)
17. Does Satan actually think he might win?