After requesting facebook permissions we can check facebook permissions status using following code.

[FBRequestConnection startWithGraphPath:@"/me/permissions" completionHandler:^(FBRequestConnection *connection,id user, NSError *error) {
    NSNumber *permInbox = [[[user valueForKey:@"data"] objectAtIndex:0]valueForKey:@"read_mailbox"];
    NSNumber *permEmail = [[[user valueForKey:@"data"] objectAtIndex:0]valueForKey:@"email"];
    NSNumber *permlocation = [[[user valueForKey:@"data"] objectAtIndex:0]valueForKey:@"user_location"];
    NSNumber *appInstalled = [[[user valueForKey:@"data"] objectAtIndex:0]valueForKey:@"installed"];
    if (permEmail ==[NSNumber numberWithInt:1]&& permInbox ==[NSNumber numberWithInt:1]&& permlocation ==[NSNumber numberWithInt:1]) {

        NSLog(@"%@",appInstalled);
                    // here proceed or check and print all permissions status
    }else
        // here code for request permission
}];