one XCode Project multiple iPhone apps
Each target needs its own Info.plist. And each Info.plist must have a different Bundle Identifier set. Easiest way to check is Project -> Edit Active Target, then go to the Properties tab and check the value at "Identifier". It's important that each target has a different identifies, because that is how Xcode/iPhone identifies an app. If you have several targets all using the same Bundel Identifier they will overwrite each other on install.
You need different Info.plist files, each specifying a different Bundle Identifier, to uniquify them. Otherwise, they each look the same to the device, which will just clobber one for the other.
Right-click on your build target and select Get Info. Click the Build tab, and scroll down to the build setting "Info.plist File" in the "Packaging" section. Set that to a different plist for each target you have.