How to copy Elements of Scenes between projects

I have problem. I have 3 diffrent versions of 1 Project and i need to merge them without overriding scene objects. I tried i think anything, even tried to launch 2 instances of Unity and also have tried using unity package, always my copied scene was changed with new one.

You can’t merge binary files. You’ll have to manually ‘merge’ the objects in the scenes. Rename the scenes to something unique and import them using a unity package. Then manually copy and paste things into the final scene. In the future you should use something like git to maintain versions of a single project.