Reference by Instance ID?

Can you reference an object at runtime by instance ID? If not, what's the use of an instance ID?

No, don't think you can get an object by instance id (unless you have a map of instance id to object and put every object in the game into it)

Mainly it's used by the engine, but other uses are that it's used for GetHashCode, which in turn means that hashtables and dictionaries work without collisions, as well as general uses for debugging so you know which object is which

use EditorUtility.InstanceIDToObject