I am about to buy a PS4 and I am just wondering whether there is a way to change the PS4 region/locale. I am not talking about the PSN region which I know can't be changed. I mean the PS4 region. I currently own the XBOX 360 and you can change the region/locale through system settings. When you change the XBOX 360 locale, the in-game flag also changes, e.g. if I am playing ultra street fighter 4 and my locale is set to US the flag within the game would be of US and when I change the locale the flag also changes which allows me to play people with different regions.
The PS4 is region free. Region is based exclusively on your PSN account with the rare exception of content that includes IP level filtering to determine where in the world your device is physically located (eg, Netflix) or latency values to determine if you can utilize the content (eg, PlayStation Now). Beyond this Sony has indicated that they will allow a publisher to limit their software to a particular region, but that limitation is controlled by the PSN profile, not the hardware.
If you want to play players limited to a different region, you will need to setup a separate PSN account for that region.
The only exception to this I think is DVD/BluRay region restrictions, but that is a separate issue.
Not exactly sure what you want from the description. If you want to play multiplayer games with people of different regions I think that's only related to the PSN network you're in. Changing language in PS4 will only change its interface language and will have nothing to do with games themselves. You can easily register for an account in another PSN network, and share games across different accounts though. This won't cost you extra money. However be ware that what server you play on essentially depends on game developers. Some games might just connect you to the nearest server but some might restrain you to the region of the game you bought. Maybe Ultra Street Fighter on Xbox 360 works depending on system locale but I doubt many PS4 games work this way.