How get object, if i know coordinates?

If you need to get objects by position it would be a good idea to keep a list of relevant objects, to speed up the process. The brute force method would be this:

 Vector3 position = new Vector3(3,3,3);
    GameObject[] objs = GameObject.FindSceneObjectsOfType(typeof(GameObject));
    GameObject myObject = null;
    foreach (GameObject go in objs) {
      if (go.transform.position == position) {
        myObject = go;
        break;
      }
    }

But this would be a rather slow solution. As I said you can improve it to only search the relevant objects of your scene.

An object doesn't have a normal. Only surfaces/polygons do. You can get an objects up, right and forward axis. So if you have a plane and know in which direction the planes normal is pointing you could use that.

As an alternative solution to what spree suggested, if the object has a collider, you could use Physics.OverlapSphere to return an array of the objects at that position.