It's public: https://discord.gg/qYWxqva
They change the invite code every week, so better be quick ;-)
Not currently. It's a much requested feature, but the devs aren't working on it yet, and no idea whether it's going to be prioritized in the future.
Some apps are implementing it though, and there are browser plugins (tampermonkey scripts) achieving it as well: https://greasyfork.org/en/scripts/469297-block-lemmy-instances (using that myself to block lemmynsfw.com)
I can reach it just fine. Maybe you need to flush your cache / DNS?
Generally speaking though, unless they have provided alternative means of contact and you saved them prior to the outage, there's nothing you can do. Same if they decide to shut down - the instance and your account would be lost, and that's that.
Just use the 1.1.1.1 app, or on your computer (or router) change the DNS to 1.1.1.1
Indonesia is soft blocking via DNS only, very easy to bypass.
Insights by Ground AI
Do yourself a favor and block this trash AI news aggregator, they provide no value.