Base SDK 3.0 to SDK 4.0

Question

I installed SDK 4.0 and found that I lost access to all previous SDK versions prior to 3.2.

I have found a link to download SDK 3.1.3 so I have both .dmg install fil

Answer 1

The terminology is confusing but once you understand this it's easy.

The 'Base SDK' is just the version of the SDK that you are compiling against. So you can use any classes, properties, or methods in the Base SDK.

The Deployment Version is earliest version of the OS that you want users to be able to run your code against. If you use a feature available in the Base SDK version but not in the Deployment version then your code will launch on both versions but will crash on the earlier OS version when you use the new feature, so you need to check if the new feature is present if you want to do this.

So you don't need Base SDK of 3.0 to run on 3.0 - just set Base SDK to 4.0 and Deployment Version to 3.0 and don't use any features of the SDK that weren't present beyond 3.0.