the goddess is probably using internet explorer
and quite hilarious that our slime saint can just hop in and out of the chat room with the goddess like it's a Discord server, while others, even the other saints can't even hear her voice
probably not
he is not a real historical figure, so the chance of him existing here is low
even if he exists, he would still just be a kid somewhere, consider his lord Yukimura is still a toddler (assuming that's him at page 12)
it's not about belief
it is just that the life here is too comfortable to live compared to when they lived in Hongan-ji temples (or most of the villages outside of Shizuko's influence, which results in the spies deserting/not reporting back.
it's not like this sword really important in any way; they already have tons of relic, artifact, legendary weapons back home
and Urza already had her own person sword; you may forgot it because it only appears in a few chapters