Keep main scene and load Prefabs from other scenes as assets

I know this has been asked before, but all the old answers popping up seems to give me webserver errors within this forum.

Can anyone post an example of how I can maintain the mainloop/scene, load 2 other scenes (with their own Prefabs, Scripts and Textures included) and then use them dynamically in the mainloop?

I know how to load a scene, but my Unity keeps locking up/crashing when I test it, so its darn hard to figure out where it crashes as NOTHING responds and I have to load Unity editor for each try.

I’ve concluded that you cannot load .unity3D files without loosing the previous in memory, so there is no way to preload/additive load extra unity prefabs without using the normal PRO only assetsbundle load function.

Its okay, but not very clear anywhere. Including the license/edition comparing page.

But I mark this question as closed now as no one else seems to have better answers? :o)