1) What is the likelihood of something happening for which you have no data that would allow you to predict it?
Do you mean anything that fits that criteria, or a given thing that fits it? I find it quite likely that there is a large number of things that are true that we have no realistic way of finding out, but it’s dwarfed by the number of things that are false that we have no realistic way of finding out. If there are five things that are true that you can’t verify, so you decide to believe five unverifiable things, it just means you’ll be wrong ten times instead of five.
Do you mean anything that fits that criteria, or a given thing that fits it? I find it quite likely that there is a large number of things that are true that we have no realistic way of finding out, but it’s dwarfed by the number of things that are false that we have no realistic way of finding out. If there are five things that are true that you can’t verify, so you decide to believe five unverifiable things, it just means you’ll be wrong ten times instead of five.