How hot update Game in IOS?

HI guys
This want to use UE4 to do such a app in IOS.
and , I will make Some of the game level . However, considering the package size (maby 500M-1G). i want save the level data in my Server machine . the app is only a very simple app. so it`s size is very small (maby 30-50M) .
Then ,when users install the app . they can chose which game Level to download.

. i cant Modify the game .Because ios Sandbox. So , its any way to let ue4 openLevel with the path of "Document , temp ,or cache directory?

have u got a solution?