Tried code below with storyboard, app starts with modal view controller:
AppDelegate.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
[self.window makeKeyAndVisible];
[self.window.rootViewController performSegueWithIdentifier:@"modalSegue" sender:self];
return YES;
}
Segue configuration from start view controller to modal view controller: