We are still working on tablet support. It will be part of an upcoming update.

Well, i do understand something in android developing - at one one hand thats really a kind of insane mess ... but at other hand i cant understand whats wrong with your manifest that g.play cant allow me to install ff14

I'm not sure why you think it's 'an insane mess'. Development could not finish in time for our initial release, and we did not want to delay by a couple months.

You can test out what is available for tablets as a preview with Nightly, our developer channel builds at http://nightly.mozilla.org

I compared development for android with a mess because of many known irrational problems, especially native develop ;)