World Adventures and Into the Future are travel locations, whatever family you are playing at the time can travel there via cell phone for China, Egypt and France or by the time portal for Oasis Landing, so you could visit all four in one game, or just some, it's up to you.
You can purchase vacation homes using the phone in all of them, for the first three you need to go adventuring until you get a level 3 visa but for Oasis landing if you have the money you can do that straight away, there is also no time limit in the future so you could live there indefinitely if you wanted, it doesn't have all the rabbit holes for jobs and no school though.
If you move town via the cell phone your sim will have all the traits, skills, degrees and even job they had in the old town, they just lose any relationships with sims outside the household in the previous town, alternatively you can save them to the household bin in edit town and they will still keep their traits degree and skills when you place them again. But as before no ties outside the household and also no job this way.
