Scoring system by pressing a series of particular keys

It's my suggestion:

 [SerializeField] KeyCode[] keys; // to make sequence in unity editor
 void Start()
     {
         StartSequence(keys);
     }
 void StartSequence(KeyCode[] keys)
     {
         StartCoroutine(WaitForInput(keys, 0)); // start reading first key from sequence array
     }
 
     IEnumerator WaitForInput(KeyCode[] key, int index)
     {
         while (!Input.anyKeyDown) // wait for key pressing
         {
             yield return null;
         }
         if (Input.GetKeyDown(key[index])) // if correct key is pressed
         {
             if (index + 1 >= key.Length) // check if is there any key read, if no - give score
                 EndOfSequence(); // random void where you can put score funcionallity
             else
                 StartCoroutine(WaitForInput(keys, index + 1)); // go for next key in array sequence
         }
         else // if it's bad key, return to first key of sequence.
         {
             StartCoroutine(WaitForInput(keys, 0));
         }
     }

Here's my suggestion. Code compiles, runs and will reset if you hit the wrong key.

We do this by creating an array of keys, and an index integer to hold our place in the array. When we hit a correct key, we increment through the array. If we hit a wrong key, we revert back to place 0, the beginning of the array.

In the inspector panel, you can create as many key inputs to run through as you want.

     //Our keys to use
     public KeyCode[] Keys;
 
     //Integer used to index the array
     int Check;
 
     // Update is called once per frame
     void Update()
     {
         InputCheck();
     }
 
     void InputCheck()
     {
         //Making sure we don't go above the number of keys (preventing index out of range issues)
         if (Check <= Keys.Length - 1)
         {
             //If we pressed down the right key, increase
             if (Input.GetKeyDown(Keys[Check]))
             {
                 Debug.Log("CORRECT KEY!");
 
                 //Increase check, so we check against the next key
                 Check++;
 
                 //If we've hit all keys successfully
                 if (Check == Keys.Length)
                 {
                     //Score increase!
                     Debug.Log("ADD SCORE!");
                 }
             }
             //If we pressed down a key, and the key is not the correct key
             else if (Input.anyKeyDown && !Input.GetKeyDown(Keys[Check]))
             {
                 Check = 0;
 
                 Debug.Log("WRONG KEY!");
             }
         }
     }