How do you check if an instance of an object has been clicked on more than once?

 1. Add an EventSystem in your scene (GameObject > UI > EventSystem)

 2. According to the type of your objects which must be clicked:

     a) 3D objects : Attach a Physics Raycaster to the event system

     b) 2D objects : Attach a Physics 2D Raycaster to the event system

     c) UI objects : Attach a Graphic Raycaster to the event system

 3. To each of the objects that should be clicked:

     a) 3D objects : Attach a Collider

     b) 2D objects : Attach a 2D Collider

     c) UI objects : Make sure the object has an image with RaycastTarget enabled

 4. Create a new C# script called ClickTarget.cs with the following class, and attach the component to each objects that should be clicked:

 using UnityEngine;
 using UnityEngine.EventSystems;
 
 public class ClickTarget : MonoBehaviour, IPointerClickHandler
 {
     public event System.Action<ClickTarget> OnClicked;
 
     public void OnPointerClick( PointerEventData eventData )
     {
         if ( OnClicked != null )
             OnClicked.Invoke( this );
     }
 }

 5. Create a new C# script called Combo.cs with the following class:

 using UnityEngine;
 
 [System.Serializable]
 public class Combo
 {
     public ClickTarget[] Targets;
     public UnityEngine.Events.UnityEvent OnComplete;
     public float maximumClickInterval = 0.5f;
 
     private int index = 0;
     private float lastClickTime;
 
     
     public void HandleTarget( ClickTarget target )
     {
         if ( Targets.Length < 1 || Targets[index] == null )
             return;
 
         // Reset timer if clicked too late
         if ( Time.time > lastClickTime + maximumClickInterval )
             index = 0;
 
         // Correct target clicked
         if ( target.GetInstanceID() == Targets[index].GetInstanceID() )
             index++;
         else if ( target.GetInstanceID() == Targets[0].GetInstanceID() )
             index = 1;
         else // Wrong target
             index = 0;
 
         if ( index == Targets.Length && OnComplete != null )
         {
             OnComplete.Invoke();
             index = 0;
         }
 
         lastClickTime = Time.time;
     }
 }

 6. Create an empty gameobject with the following ClickTargetsManager script:

 using UnityEngine;
 
 public class ClickTargetsManager : MonoBehaviour
 {
     public ClickTarget[] Targets;
     public Combo[] Combos;
 
     private void Start()
     {
         for ( int i = 0 ; i < Targets.Length ; i++ )
         {
             Targets[i].OnClicked += OnTargetClicked;
         }
     }
 
     private void OnTargetClicked( ClickTarget target )
     {
         for ( int i = 0 ; i < Combos.Length ; i++ )
         {
             Combos[i].HandleTarget( target );
         }
     }
 }

 7. In the inspector, select the ClickTargetsManager, and drag & drop all the objects holding the ClickTarget script into the Targets array

 8. Create your combos by dragging & dropping the gameobjects holding the ClickTarget script into the Targets array of each combo.

 9. Provide the function you want to call once a combo is completed the same way you do with the OnClick function of a button for example.

Please, next time, provide what you have tried so far