There is no Navy rate or rank "SW"; SW is a warfare specialty designation that stands for Surface Warfare, or one who has completed qualifications for the SW badge. It's equivalent to a submariner's dolphins badge, or an aviator's wings.

Anti-Partisan Guerrilla Warfare Badge was created on 1944-01-30.

The Enlisted Surface Warfare Specialist Designator, like all Navy Warfare emblems before it (Submarine Dolphins, SEAL Trident device, etc.) is worn on the left breast of the uniform above the ribbon devices, if any are authorized.

However, if the member is qualified in more than one Warfare Specialty, the current warfare specialty the member is working in takes precedence for uniform requirements. For example, as a Submariner, I of course had Dolphins to wear once I became Qualified in Submarines, but we did have the occasional skimmer (surface navy guy) go insane and volunteer for the Submarine Force.

If he was Qualified as an ESWS, and then subsequently became Qualified in Submarines, he would wear the Submarine Warfare badge (Dolphins) in the normal spot above the ribbon device, since he was currently serving in the Submarine Force and not the Surface Navy. The ESWS badge would then be worn underneath the ribbon device.

No. You cannot change your badge on this game. The only way is to level up or prestige.

The purpose of a badge clip is to hold a badge well often being connected a lanyard or chain. This allows for easy removal of the badge without having to pin it to a surface.