What is the code for creating and destroying instances?

what is instance_create and instance_destroy in Unity engine?

If you are looking to Instantiate (clone) objects, then you can try similar code to:

GameObject cloneOfOriginal = Instantiate(original) as GameObject;

If you are looking to Destroy objects:

Destroy(someScript);            // Destroys only the script, not the game object

Destroy(someScript.gameObject); // Destroys the game object and everything 
                                // contained in it

Destroy(this);                  // Destroys this script instance 

Destroy(gameObject);            // Destroys the gameObject that this script 
                                // instance is running on