"Work as if you live in the early days of a better nation"
What is the meaning of the torch icon in the scenario list? Recommended scenarios? Would be possible to play a scenario not in the list?
They are recommended configurations. The ones without the touch are still tested and viable but may be a little more advanced.
In addition there are huge numbers of viable scenarios that are unlisted. The way the scenario page works is that you can pick any viable three player combination and then add any other factions to it. As long as you work from a viable seed you'll be fine.