Am I able to use functions and classes that come from unity? I know I can use Vector3 etc but can I use something like Gameobject.parent or other things? 

Yes, the majority of things in Unity you can use; though there are some exclusions such as the UI elements.

So in theory I can do stuff like parent a peice of scrap (dropped on the floor) to me so it follows me? Aka like regular unity functions