What needs to happen in order for Symbian OS to be able to maintain a significant market share along with Android and iPhone? Also would there be more innovation taking place as a result of pressure from a third major competitor?
What happens if United States goes ahead with Operation Downfall but gets defeated by Japan in the end? Is that something within the realm of possibility?
What would have happened if Luther was never excommunicated by the Catholic Church for the 95 theses? What would be required for that to not happen? A more liberal pope?
The challenge is to have American and British English become only 50 percent or less mutually intelligible sometime during the 20th century. What would it take for that to happen?
Is there any possible way that the European powers could have held onto their colonies in Africa and Asia after WWII? Perhaps the United States would need a different foreign policy for that to happen.
What if instead of petering out in 1975-1980, the hippie movement were to continue into the present? What butterfly effects would be needed for that to happen?
What would it take for Russia to only expand as far east as the Ural Mountains? Also what would be the butterfly effects if Russian territory stayed only within Europe? I'd imagine that most of OTL Asian Russia would become like the Amazon Rainforest with lots of uncontacted peoples.
What would happen if Linear B remained in use and were adopted by the Romans? Did Linear B have more characters than the later Greek alphabet? If so, would that mean less literacy in Rome and during the rest of Western history given that it's harder to learn?
The challenge is to have the Middle East except for Persia and Arabia become majority Gnostic by 600 while still having Europe and North Africa become majority Nicene Christian as in IOTL. Would that necessarily require the overthrow of Roman or later Byzantine authority? Or could some sort of...
What would happen if Jim Crow laws had been overturned but it was still legal for businesses but not government run places to refuse service to people based on race?
Is a Communist revolution in Saudi Arabia something plausible? If so, what would it take for it to happen? The challenge is to have it happen sometime in the 1930s or 1950s. What would be the effects on Islam if such a government adopted state atheism? Would Salafism have less influence?