Logout of Social Networks from iOS application

In my app i am using Google, face book login. I was able to login properly but when i try to log out from Google , face book i am using following code.But my problem is even if i log out from my app.

When i click on login buttons it is asking permissions not login screen. Even if i log out from my app, Do i need to log out in safari browser (clear cookies in settings) or device social apps, or do i need to do log out from Appdelegate.

What to do to complete logout from app it self.

[[GPPSignIn sharedInstance] signOut];

//facebook
FBSession* session = [FBSession activeSession];
[session closeAndClearTokenInformation];
[session close];
[FBSession setActiveSession:nil];
NSHTTPCookieStorage* cookies = [NSHTTPCookieStorage sharedHTTPCookieStorage];
NSArray* facebookCookies = [cookies cookiesForURL:[NSURL URLWithString:@"https://facebook.com/"]];

for (NSHTTPCookie* cookie in facebookCookies) {
    [cookies deleteCookie:cookie];
}