As title says, i want to start self hosting but i have a lot of questions about it. For more context, i want to self host XMPP, matrix, Immich, an email, forgejo and a minimal website. i want to ask you:

1. Where should i buy my domain and are there any things i should be careful about?

2. does the end of my domain (idk the specific name but .XYZ) matter at all?

3. I get that i should use a used PC (i have none lying around), but how old?

4. Am i willing to self host too much stuff?

5. Can i use Gentoo, Devuan, or other non-systemd distros as an OS?

Sorry for the noob questions but i struggle to find answers online, feel free to tell me to RTFM _;
Also, i have experience with Linux as a desktop OS, more specifically 3 years, one of which mostly in gentoo, but i’ve daily driven Arch, Artix, Debian, Void among others