[TUTORIAL] More-or-less Catch-All Tutorial

This guide only applies to 3DS system versions 4.0-10.3, and the CFW process only applies to system versions 4.0-9.2.
The general roadmap is: Browserhax & Menuhax > emuNAND prep > CakesFW > Unlinking. The last sections of the guide are optional and deal with important homebrew and MultiNAND creation, respectively. Downgrading is only necessary for 9.3+ systems, and Upgrading is entirely optional.
If a system firmware update has been released and you're on a firmware above 9.8 and below...

[TUTORIAL] More-or-less Catch-All Tutorial