GreedyGameAds.Instance.LoadRewardAd("SDK X Reward adUnit");

 // To check if Reward is loaded
 GreedyGameAds.Instance.rewardAd.IsLoaded

using UnityEngine;
using GreedyGame;

 public class GreedyGameAdsDemoScript : MonoBehaviour
 {

    private void Start()
    {
        //after Initialize the GreedygameAds sdk
        this.LoadReward();
    }

    public void LoadReward()
    {
        GreedyGameAds.Instance.LoadRewardAd("SDK X Reward adUnit");
    }

 }

 GreedyGameAds.Instance.ShowRewardAd(GetReward);

 //callback when user close the reward Ad
 public void GetReward(bool canReward)
 {
     //canReward = true if player watched full Ad
     //canReward = false if player closed the Ad inbetween 
 }

 public void WatchAdForExtraCoins()
 {
     . . .
     . . .
     this.ShowReward();
 }

 //After RewardAd Method Loaded
 public void ShowReward()
 {
    GreedyGameAds.Instance.ShowRewardAd(GetReward);     
 }

 public void GetReward(bool canReward)
 {
     if(canReward)
     {
        // Give Reward
     }
     else
     {
        // No Reward 
     }

  }
    

Optional Show Reward Ad using LAMBDA function

GreedyGameAds.Instance.ShowRewardAd((bool canReward) =>
{
     if(canReward)
     {
        // Give Reward
     }
     else
     {
        // No Reward 
     }
 }

To further customize the behavior of your ad, you can hook into a number of events in the ad's lifecycle: loading, opening, closing, and so on. Listen for these events by registering a delegate for the appropriate EventHandler, as shown below

 GreedyGameAds.Instance.rewardAd.OnAdloaded
 GreedyGameAds.Instance.rewardAd.OnAdFailedToLoad
 GreedyGameAds.Instance.rewardAd.OnAdOpened 
 GreedyGameAds.Instance.rewardAd.OnAdShowFailed

  public void LoadRewardAd()
  {

       GreedyGameAds.Instance.LoadRewardAd("SDK X Reward adUnit");  

       // Called when an ad request has successfully loaded.
       GreedyGame Ads.Instance.rewardAd.OnAdloaded += this.HandleOnAdLoaded;

       // Called when an ad request failed to load.
       GreedyGameAds.Instance.rewardAd.OnAdFailedToLoad= this.HandleOnAdFailedToLoad;

       // Called when an ad is clicked.
       GreedyGameAds.Instance.rewardAd.OnAdOpened+= this.HandleOnAdOpened;
      
       // Called when the ad Failed to show
       GreedyGameAds.Instance.rewardAd.OnAdShowFailed += this.HandleOnAdShowFailed;

   }


  public void HandleOnAdLoaded()
  {
      MonoBehaviour.print("HandleAdLoaded event received");
  }

  public void HandleOnAdFailedToLoad(string error)
  {
      MonoBehaviour.print("HandleFailedToLoadAd event received with message: " +error);                           
  }

  public void HandleOnAdOpened()
  {
      MonoBehaviour.print("HandleAdOpened event received");
  }

  public void HandleOnAdClosed()
  {
      MonoBehaviour.print("HandleAdClosed event received");
  }

  public void HandleOnAdShowFailed()
  {
      MonoBehaviour.print("HandleAdShowFailed event received");
  }