Do people who immigrate to the USA from Guam need a VISA/ Passport?

US citizens can live anywhere in the US - they are not "immigrants." It would be a good idea to have your US passport as proof of US citizenship, because you are going to have to prove you're a citizen. Expect to need a great deal of money to relocate to the Continental US, even more for high-cost Hawaii.

They don't need a visa but unless they're traveling directly without leaving US authority zones they'd need a passport.

They can move to any state. They do not need a visa. Technically, a passport isn't need either, but it's a good idea to have one, because of the possibility of needing to stop in another country if there are problems with the airplane or the weather.

No you do not as you are a US Citizen. You can move to any state or other US territory you want.  BUT when traveling most flights do not go straight from Guam to Hawaii or the mainland so you can need a passport as your layover can be in Japan. 

Guam is a Territory of the US won during the Spanish-American War. I don't need a passport to go to Guam. You don't need a passport to come here. Imperial Japan invaded Guam but Imperial Japan no longer exists.

they might, i would talk to immigration about it