: Capturing flags in Conquest or Operations provides significantly more XP than kills alone.
That being said, here are some cheats and codes that can unlock all weapons in Battlefield 1: Battlefield 1 Unlock All Weapons Cheat
True "unlock all" cheats for multiplayer are almost always temporary visual hacks. You see the gun equipped, but the server may still need a "kill confirm" to register damage. : Capturing flags in Conquest or Operations provides