ViewController login page for different accounts does not work

Question 1. In my FIREBASE data, I hope that different values ​​of "Safety-Check" lead to different VIEWs.
Here is my code,
Can someone give me some advice?

 Database.database().reference().child("ID/\(self.uid)/Profile/Safety-Check").observeSingleEvent(of: .value, with: {
                                (snapshot) in
                    let cheak = "Safety-Check"
                    if cheak == "admin" {
                        
                        if let viewController = self.storyboard?.instantiateViewController(withIdentifier: "AdminVC") {
                          UIApplication.shared.keyWindow?.rootViewController = viewController
                            self.dismiss(animated: true, completion: nil)
                    }
                    if cheak == "ON" {
                        if let viewController = self.storyboard?.instantiateViewController(withIdentifier: "MainTabBarController") {
                          UIApplication.shared.keyWindow?.rootViewController = viewController
                            self.dismiss(animated: true, completion: nil)
      
                    }else{
                        if let viewController = self.storyboard?.instantiateViewController(withIdentifier: "SignUpViewControllerID") {
                          UIApplication.shared.keyWindow?.rootViewController = viewController
                            self.dismiss(animated: true, completion: nil)
                        }
                    }
                    }
                    }
                })
            })
    }
}

Question 2. Yellow Warning: ‘keyWindow’ was deprecated in iOS 13.0: Should not be used for applications that support multiple scenes as it returns a key window across all connected scenes.

How should I modify it to fix this problem?

UIApplication.shared.keyWindow?.rootViewController = viewController

>Solution :

Use below function the get the window :

func GetWindow() -> UIWindow? {
    
    if #available(iOS 13.0, *) {
        let sceneDelegate = UIApplication.shared.connectedScenes
            .first?.delegate as? SceneDelegate
        let appDelegate = UIApplication.shared.delegate as? AppDelegate
        return sceneDelegate?.window ?? appDelegate?.window
    } else {
        
        let appDelegate = UIApplication.shared.delegate as? AppDelegate
        return appDelegate?.window
    }
}

usage of above function :

 if let window = GetWindow() {}

With respect to your case :

GetWindow()?.rootViewController = viewController

So replace these lines :

 UIApplication.shared.keyWindow?.rootViewController = viewController
                            self.dismiss(animated: true, completion: nil)

With :

GetWindow()?.rootViewController = viewController
GetWindow()?.makeKeyAndVisible()

And you don’t need to dismiss as it set a new root view controller with this code.