Is there any way to make apps with fixed vertical orientation rotate?
An iOS app can be programmed to support any one, more or all of the following orientation modes:


Portrait
Upside Down
Landscape Left
Landscape Right


If talking about the portrait mode(s), while the apps targeting iPhone are generally configured to only support Portrait mode (front camera at the top), the ones for iPad support both Portrait and Upside Down (front camera at the bottom) mode.

If the app is question is programmed to only support Portrait mode, there is no way for the user to also make it work in Upside Down mode.