Can I use the features of AR2 Gen1 without the use of Unity or Unreal? I see that SDK exists only for game engines. How can I have an API to spatial mapping or plane detection directly? I am not developing a game
Snapdragon Spaces is OpenXR standard compliant. You can in theory create your application running native following the OpenXR standard.
While going native is an option, I'd recommend using either Unity or Unreal - they are not "just" for games. We do not have a native SDK available, and do not officially provide support on developing a native application.
A good starting point would be the Khronos Hello XR sample app: OpenXR-SDK-Source/BUILDING.md at main · KhronosGroup/OpenXR-SDK-Source · GitHub