Respawn from falling off world!

  public Transform spawnPoint;//Add empty gameobject as spawnPoint
  public float minHeightForDeath;
  public GameObject player; //Add your player
  
  void Update()
 {
   if(player.transform.position.y < minHeightForDeath)
       player.transform.position = spawnPoint.position;
 }
 
 //There are many ways to do this. This is just one way
 //Try not to use Physics if you don't need it(there is a way to 
 //do this by using Physics)

make a new c# script and name it respawn, copy and paste this >>

 using UnityEngine;
 using System.Collections;
 
 public class respawn : MonoBehaviour {
     public float threshold;
 
     void FixedUpdate () {
         if (transform.position.y < threshold)
             transform.position = new Vector3(0, 0, 0);
     }
 }

then drag that script onto your character..the primary parent object. THEN go to the inspector and set the threshold to something below the floor....on a standard setup a number like -20 or -50 will work great.

 float fallZone = -10f;
 public Transform playerSpawnPoint = null; //create an empty gameobject and assign it to this script  in the inspector   

 void Update(){

 if(player.transform.position.y < fallZone) //Assuming its a 2D game
 {
  player.transform.position = playerSpawnPoint.position;
 }
 }

suppose the platform size is 300 on the x axis , y axis and anything on z axis

// EndGame() is a function defined by me to end game on falling out of the platform stored in a script called GameManager

//

public Rigidbody player;

public float lastposition;

public GameObject gameover;

bool gameHasEnded = false;

public void Resume()

{

if (player.position.y < 0.1f) // player dies if falls below 0.1 on y axis

{

lastposition = player.position.z;

FindObjectOfType ().EndGame(); .

transform.position = new Vector3 (0, y ,lastposition);

}}

public void EndGame ()

{

if (gameHasEnded == false)

{

gameHasEnded =true;

respawn ();

gameover.SetActive(true);

}

// THIS SCRIPT HAS TO BE ATTACHED TO THE PLAYER By default it will set the offset to be -50 on the y from the starting position

 using UnityEngine;
 public class PlayerRespawn : MonoBehaviour {

 Vector3 _InitialPos; // Starting position of the player
 float _YOffset;

 void Start () {
     _InitialPos = transform.position;
     _YOffset = _InitialPos.y - 50;
 }
 
 void Update () {
     if (_InitialPos.y < _YOffset)
     {
         transform.position = _InitialPos;
     }
 }

}