Why a value from a script attached to prefab cannot be passed to another script?

Code (CSharp):

1.  
2. if (HomeScreen.HomeScreenInstance.Deletevalue == true)
3. {
4.              
5.   go.transform.GetChild(1).GetComponent<Button>().gameObject.SetActive(true);
6.   string buttontxt = go.transform.GetChild(0).GetComponent<Text>().text;
7.  
8.  //OnClick added to the button via code
9.  go.transform.GetChild(1).GetComponent<Button>().onClick.AddListener(() =>   DeleteGivenNote(buttontxt));
10.  
11.  }
12.  else
13.    {
14.     Debug.Log("Delete Value..... " + HomeScreen.HomeScreenInstance.Deletevalue);
15.    }
16.  
17.  
18. public void DeleteGivenNote(string btntxt)
19. {
20.  
21.   string foldername = LoaditemsDropdown.options[LoaditemsDropdown.value].text;
22.  
23.   int btnindex = ButtonDetailsClick.ClickInstance.buttonIndex;
24.   Debug.Log("Button Index and btn text = " + btnindex+" :: "+btntxt);
25.   if (File.Exists(Application.persistentDataPath + "/" + foldername +"/"+btntxt+ ".json"))
26.     {
27.      
28.       infos.Remove(infos[btnindex]);
29.       // File.Delete(Application.persistentDataPath + "/" + foldername + "/" + btntxt + ".json");
30.       // Load();
31.       for (int i = 0; i < infos.Count; i++)
32.        {
33.           Debug.Log("infos after" + infos[i]);
34.        }
35.     }
36.  
37. }
38.  

The below I added in the prefab and attached it to the prefab button Onclick.Dragged and dropped the DeleteIndex() method to the button.

Code (CSharp):

1. [HideInInspector]
2.     public int buttonIndex=0;
3.  
4.     // Start is called before the first frame update
5.     void Start()
6.     {
7.         ClickInstance = this;
8.  
9.     }
10.  
11.     // Update is called once per frame
12.     void Update()
13.     {
14.    
15.     }
16.    
17.     public void DeleteIndex()
18.     {
19.         buttonIndex = this.transform.GetSiblingIndex();
20.         Debug.Log("Indexxx = " + buttonIndex);
21.     }
22.  

Even though the Indexxx value gets printed it is giving 0 value in the DeleteGivenNote method.Is this because I have given both methods to the same button.One Via code and other dragged and dropped.How to get the Sibling Index of a prefab it it is instantiated under a transfrom many times.