Edit properties of certain list items,Changing properties of objects in a list (c#)

Questions & Answers
1

I would like to create an indefinite amount of GameObjects (Spheres). During the game, certain actions will create a new sphere. To keep track of the spheres I would like to make a list since using arrays requires me to know how many spheres there are going to be.
Using the following script, I am able to create the spheres and add them to a list. If I try to change the position of a certain GameObject on the list (using Listname[2].transform.position.set(x,y,z) absolutely nothing happens. How can I change the properties of a certrain GameObject in a list?
Example:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class Player : MonoBehaviour {

	public GameObject playerSeg;
	public int segNum, p = 1;
	public Vector3 pos = new Vector3(1,1,1);
	private Quaternion test;
	public List<GameObject> SegList;

	void Start () {
		SegList = new List<GameObject>();
            CreateSegment();

	}

	void Update () {
		SegList [1].transform.position.Set(1,3,1);
	}

	void CreateSegment()
	{
		SegList.Add (Instantiate (playerSeg,pos,test));
	}


	
}
2

@trodd0
Assuming GameObject has some kind of an identifier property, try:

void Update (int id, Vector3 newPos) 
{
     SegList.Find(o => o.GameObjectId == id).transform.position.Set(newPos);
}