Per https://bugzilla.mozilla.org/show_bug.cgi?id=1177970#c13, it should be possible to figure out what version of the app (not the midlet, but the FxOS app that runs the midlet) you have installed. Ideally, FxOS would expose this in some kind of management interface, but it doesn't. So the app should display it somewhere, perhaps in a corner of the startup splash screen?
Per https://bugzilla.mozilla.org/show_bug.cgi?id=1177970#c13, it should be possible to figure out what version of the app (not the midlet, but the FxOS app that runs the midlet) you have installed. Ideally, FxOS would expose this in some kind of management interface, but it doesn't. So the app should display it somewhere, perhaps in a corner of the startup splash screen?