Email requirements for registration are set per-instance. Beyond that, it’s my understanding that only a user’s existence is shared across instances, in order to attach you to your content. Your registration details stay on the instance you belong to.
All you have to do is host your own instance and other instances you connect with mirror their content to yours. It’s part of the design of the protocol to help reduce user load on any particular server. While users can see content from any connected instance, direct communication happens almost exclusively with their own instance.
Definitely this. If you’re absolutely sure you can’t change config on the router, then you just treat it like a modem. Let it serve up one, single DHCP lease to your own router and run your network off of that.
Definitely a result of recency bias here, but in a couple of scenes in Tears of the Kingdom, Ganondorf is flanked by two female Gerudo with unique outfits. If you translate the Hylian text on these outfits, they say Koume and Koutake.