How to click objects in a specific order to change scene

The community is not supposed to make the job for you. The asker is supposed to provide what he has tried so far. But since I'm in good mood, I've made something for you.

1st step : Setting up your scene

   1. Select your camera and click on Add component in the inspector and type physics in the search bar.

      • If you want to click on 3D models, select the Physics Raycaster

      • If you want to click on 2D sprites, select the Physics 2D Raycaster

      • If you want to click on UI elements, don't add any component

   2. Click on the GameObject menu option at the top of the Unity window, and select UI > Event System

   3. Create an empty gameobject called ClicksManager for instance (use the GameObject menu)

2nd step : The clickable objects

In your scene, create the elements which will be clicked.

      • If you want to click on 3D models (such as a cube, a sphere, ...), they must have a Collider component

      • If you want to click on 2D sprites, they must have a 2D collider component

      • If you want to click on UI elements, the image / raw images must have Raycast target checked

3rd step : The scripts

   1. Create a new C# script called ClickTarget.cs and put the following code inside.

 using UnityEngine;
 using UnityEngine.EventSystems;
 
 public class ClickTarget : MonoBehaviour, IPointerClickHandler
 {
     // Define the function signature used to invoke a specific event
     public delegate void OnTargetClickedEventHandler( ClickTarget target );
 
     // Define the event invoked when the target will be clicked
     // The event will warn the entities subscribing to this event that the target has been clicked
     public event OnTargetClickedEventHandler OnTargetClickedEvent;
 
     // Detect when the Event System of Unity has detected a click on the target
     public void OnPointerClick( PointerEventData eventData )
     {
         // Invoke the event
         if ( OnTargetClickedEvent != null )
             OnTargetClickedEvent( this );
     }
 }

   2. Create a new C# script called ClicksManager.cs and put the following code inside.

 using UnityEngine;
 using UnityEngine.SceneManagement;
 
 public class ClicksManager : MonoBehaviour
 {
     // Drag & Drop the objects with the `ClickTarget` component
     [SerializeField]
     private ClickTarget[] targets;
 
     // Each target will have an index (based on its position in the previous array)
     // This variable will indicate which target must be clicked
     private int expectedTargetIndex;
 
     // Called when the scene starts
     private void Start()
     {
         expectedTargetIndex = 0;
 
         // For each target, call a function when they are clicked
         for ( int i = 0 ; i < targets.Length ; i++ )
         {
             // You have to declare a temporary index to prevent the "closure problem"
             int closureIndex = i;
 
             targets[closureIndex].OnTargetClickedEvent += ( target ) => OnTargetClicked( target, closureIndex );
         }
     }
 
     // Function called when a target is clicked
     private void OnTargetClicked( ClickTarget target, int index )
     {
         Debug.Log( target.name + " has been clicked!" );
         if ( index == expectedTargetIndex )
         {
             Debug.Log( "The correct target has been clicked" );
             expectedTargetIndex++;
             if ( expectedTargetIndex == targets.Length )
             {
                 Debug.Log( "The last target has been clicked : Loading next scene" );
 
                 // Load next scene
                 SceneManager.LoadScene( SceneManager.GetActiveScene().buildIndex + 1 );
             }
         }
         else
         {
             Debug.Log( "The wrong target has been clicked" );
             expectedTargetIndex = 0;
         }
     }
 }

4th step : Attaching and configuring the scripts

   1. Select the objects which must be clicked. Click on Add component in the inspector, and add the ClickTarget component

   2. Select the ClicksManager object and add the ClicksManager component

   3. In the inspector, you should see the Targets array. Drag & Drop, one by one the objects with the ClickTarget script. The order you assign those objects will determine the order they must be clicked when the game runs

5th step : Run the game and enjoy!

   1. Click on the Play button of Unity

   2. Click on the objects and you will see the messages in the Console tab of Unity (if you don't see it, click on Window > Console in the top menu of Unity)