What you have done seems correct. Though I haven't used VK before, I often do this to allow for Facebook and a custom URL scheme, usually based on the app's name.
For instance, I used two URL schemes here and can successfully open the app with both.
I sometimes use the URL scheme to determine when a call is not from Facebook.
if ([[url scheme] isEqualToString:@"m*****"])
{
...
return YES;
}
return [FBAppCall handleOpenURL:url sourceApplication:sourceApplication];