The Orientations property is a TFormOrientations, which is a System::Set of TFormOrientation values. You can't use Set::operator== to compare it to a single value, which is why you are getting a compiler error. However, you can use the Set::Contains() method to check if it has a given value, eg:
if (Application->FormFactor->Orientations.Contains(Fmx::Forms::TFormOrientation::Landscape)) {
//...
}
In any case, the Orientations property specifies which orientation(s) the application's Forms are allowed to take (a value of 11 has its 1st, 2nd, and 4th bits set to 1, which correspond to the Portrait, Landscape, and InvertedLandscape orientations being enabled). It does not report what the device's current orientation is. For that, use the IFMXScreenService::GetScreenOrientation() method instead, eg:
_di_IFMXScreenService ScreenService;
if (TPlatformServices::Current->SupportsPlatformService(__uuidof(IFMXScreenService), &ScreenService)) {
if (ScreenService->GetScreenOrientation() == Fmx::Types::TScreenOrientation::Landscape) {
//...
}
}