Given that we currently lack a description what is on-topic (Where is the definition of an on-topic question?) I think maybe we should make a list of things we think should be considered on-topic.
It would help for each example you provide if there can be a counter example of when a similar question strays into off-topic territory. I recommend a separate answer for each on-topic/off-topic pair so people can vote for the categories they agree with.
The examples needn't be questions that have actually been posted, or even theoretical sample question, a broad outline of a type of question will do to get things started.
I'm not suggesting this list be any sort of definitive statement of what questions are right for this site, but having a pool of ideas about what are good and bad question would go a long way to help in figuring out what should be on the help page: https://puzzling.stackexchange.com/help/on-topic
And as Emrakul pointed out, you might just want to define the sort of thing that is off-topic and should be avoided.