HOW to PlayerPrefs.DeleteAll () in that only level ? HELP

Hello buddy, I made 3 levels and each level can reset minilevels in it.

level 1 = has 6 mini levels level 2 = has 3 mini levels level 3 = has 3 mini levels

but when i reset level 2 mini level, all level will reset even level 1, i just want level 2 to reset. something wrong with this code: PlayerPrefs.DeleteAll ();

HERE'S MY LEVEL 2, LEVEL CONTROL SCRIPT

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

public class Lvl2Control : MonoBehaviour {

 public Button lv2x1, lv2x2, lv2x3;
 int levelPassed2;

 void Start () {
     levelPassed2 = PlayerPrefs.GetInt ("LevelPassed2");
     lv2x2.interactable = false;
     lv2x3.interactable = false;



     if (levelPassed2 == 19) {
         lv2x2.interactable = true;
         lv2x3.interactable = false;
     }

     if (levelPassed2 == 20) {
         lv2x2.interactable = true;
         lv2x3.interactable = true;
     }



 }

 public void levelToLoad (int level2)
 {
     UnityEngine.SceneManagement.SceneManager.LoadScene (level2);

 }

 public void resetPlayerPrefs2()
 {
               **//WHAT TO CODE HERE?? 
     //levelPassed2 = PlayerPrefs.DeleteAll ();**
 }

}

this is main level , level 1, 2 and 3

![alt text][2]

![alt text][2]

this is mini level in level 2

when I reset level 2, only level 2 minilevel 2.1 only can click, other 2.2, 2.3 ECT must be locked. HOW? And all minilevel in level 1 still unlocked and not locked. [2]: /storage/temp/140233-30.png