Is sharing updates illegal?

I know sharing games is illegal but what about dlc content?

DLCs and updates are also copyrighted so sharing them would be illegal.

Hey theres this emulator called retroarch it has a 3ds core and is available on android and it can run citra so would it be possible to use citra on android now if you do this?

RetroArch is not an emulator, it’s just a front-end. And no, it’s pointless that RetroArch can run on Android, you need the core being compatible with the system that you want to run the REAL emulator on it (the Citra core available on RetroArch is the same Citra for Windows/Linux/MacOS you already know and love).