90 Degree stopping rotation on y-axis issue

Hello there,

I am facing a weird rotation issue. I try to rotate a cube 90 degree around y-axis after input. It works properly on first 3 inputs but after that, it starts rotating continuously. I check rotation by angle and the issue is, if it gets negative value it spins infinitely.(Angles process like 315 -> 225 -> 135 -> 45 issue is below 45)

There is code for context;

 public class CubeMovement : MonoBehaviour {
 
     Vector3 firstPosition;
     Vector3 secondPosition;
     Vector3 initRot;
     bool flag;
     int count = 0;
     // Use this for initialization
     void Start () {
         initRot = transform.localRotation.eulerAngles;
         flag = false;
 
     }
     
     // Update is called once per frame
     void Update () {
         if (Input.GetMouseButtonDown(0)) {
             firstPosition = Input.mousePosition;
         }
 
         if (Input.GetMouseButtonUp(0)) {
             secondPosition = Input.mousePosition;
             initRot = transform.localRotation.eulerAngles;
             if (secondPosition.x > firstPosition.x) {
                 count++;
                 flag = true;
             }
             /*
             if (secondPosition.y > firstPosition.y) {
                 Debug.Log("Up swipe");
                 gameObject.transform.rotation = Quaternion.Euler(new Vector3(180, 0, 180));
             }
             else if(secondPosition.y < firstPosition.y){
                 Debug.Log("Down swipe");
                 gameObject.transform.rotation = Quaternion.Euler(new Vector3(-180, 0, -180));
             }
             */
         }
 
         //transform.rotation = Quaternion.AngleAxis(45, transform.up) * transform.rotation;
 
 
         if (flag) {
             
             if (transform.localRotation.eulerAngles.y > initRot.y - 90) {
                 //transform.Rotate(Vector3.up, Time.deltaTime * -90, Space.World);             
                 Quaternion newRotation = Quaternion.AngleAxis(-90, Vector3.up) * transform.rotation;
                 transform.rotation = Quaternion.Slerp(transform.rotation, newRotation, .05f);
                 Debug.Log(transform.localRotation.eulerAngles.y);
             }
             else {
                 if (count % 2 == 0)
                     transform.rotation = Quaternion.Euler(initRot);
                 flag = false;              
             }          
             
             //transform.localRotation = Quaternion.Lerp(transform.localRotation, Quaternion.Euler(new Vector3(0, 0, 90)), Time.deltaTime );
         }
     }
 
 }