>>28512110There are essentially two levels of "hacking your 3DS", running homebrew (through homebrew launcher) and running custom firmware.
Running stuff through homebrew launcher is the weaker option as it relies on exploits that are usually patched via system firmware updates, which means that you have to force yourself to never update and therefore leaves you unable to go online. What you can do via this metod is limited as well, you can manipulate save data or run out-of-region (physical) games but you can't pirate stuff.
Custom firmware (CFW) lets you do ANYTHING you want, including pirating, going online, fucking around with system files like a 1337 hax0r and everything you could do with the homebrew launcher. If installed properly there is next to nothing Nintendo can do about it. HOWEVER, in order to install CFW you need to be on a vulnerable system firmware version (below 11.0 if I remember correctly, there's a workaround on >11.0 versions but requires an already hacked 3DS). If you want to know if you can/how to install CFW, go to
https://github.com/Plailect/Guide/wiki 
