Samsung supports various OS environment, please check more info here

https://www.samsungdforum.com/B2B/Download/Index/SSSP4/

Yes, if you have installed the SDK, you need to uninstall it before install the other version.

No, Samsung platform only supports web technologies based apps (JS, CSS, HTML)

To download the latest SDK, go to Samsung Developer Forum > SDK > SDK Download or you can click following link, SDK Download.

https://www.samsungdforum.com/B2B/Download/Index/SSSP4

SSSP4 B2B SDK 2.4 -> SSSP4.0 -> 2017 Models

Smart B2B SDK 3.0 -> SSSP3.0 -> 2016 Models

Smart B2B SDK 2.0 -> SSSP2.0 -> 2015 Models

Smart B2B SDK 1.0 -> SSSP1.0 -> 2014 Models

For more info, please check

https://www.samsungdforum.com/B2B/Introduction/Spec/SSSP4

Samsung provides the Samsung B2B Display Apps SDK for developing Samsung B2B Display applications. It is equipped with a simulator with which the application can be tested before actually installing it in the TV, and so creating applications is easier using the SDK. The SDK also includes a WYSIWYG (What You See Is What You Get) tool that you can use for designing and creating the UI and all UI components.