SDK Manager - which APIs and which Tools to load?

I have a device with Android V4.1.2, and a device with Android V2.3.3. What versions in SDK Manager do I need to load? Presumably SDK Tools Rev 25.1.7 and SDK Platform-tools Rev 24.0.1, as theyare the latest. These I have done. I also loaded SDK Build-tools Rev 24.0.1.
Why are the earlier revisions still on the list?

I have also loaded Android 4.1.2(API 16), and Android 2.3.3 (API API 10), because of my devices.

The reason that I ask is because since loading the latest Revisions of SDK...

SDK Manager - which APIs and which Tools to load?

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