I'm trying to make an app which compatible with 3.x and 4.x iOS. But SDK 4 supports only SDK 4.x and iPad, there is no 3.x SDK for iPhone.
So I'm considering installing 3.1.3 SDK on my main workstation with 4.x SDK. I know it's possible to install multiple SDKs on a Mac, but I'm afraid any unknown problem by this.
Anyone who experienced with multiple SDKs, please let me know what happened.
While possible (just install into a different location) and without known problems on the Mac side, it is strongly discouraged.
That is, some apps show sloppy behaviour on iOS 4 - which is simply fixed by recompiling with new new SDK.
Just set the SDK base to whatever the newest (stable) version is. You can set your deployment target as low as you want, i.e. we use 4.0 base sdk and 3.0 as minimum deployment target at the moment.