how to change texture for animation?

If you name all of your sliced sprite variations the same thing you can iterate through and replace them an a late update, just put your sprite sheets in your Assets/Resources folder and you can load them at runtime:

 using UnityEngine;

 public class ReskinAnimator : MonoBehaviour
 {
     [SerializeField]
     private string spriteSheetName; //this will be the name of your spritesheet, no file extension

     void LateUpdate()
     {

          foreach (var renderer in GetComponents<SpriteRenderer>())
         {
             string spriteName = renderer.sprite.name; //finds the name of the sprite to be rendered
             var subSprites = Resources.LoadAll<Sprite>(spriteSheetName); //loads all the sprites in your new sprite sheet
             foreach (var sprite in subSprites)
             {

                 if (sprite.name == spriteName) //if the sprite has the same name as one you're trying to replace than replace it
                 {
                     renderer.sprite = sprite;
                 }
             }
         }
     }
 }