Google Play Store says it's incompatible with my Samsung Galaxy Tab 10.1
Firefox doesn't show up in the Google Play Store.
I already have Firefox 10, Firefox Beta 14, and Firefox Nightly (16.0a1 2012-06-26).
The exact model of my tablet is GT-P7500D (16 Gb model with 3G and Wifi)
Opaite Mbohovái (2)
Firefox 14 for Android is not optimized for tablets. Firefox 15 will be the first version to support it. You can keep using Nightly or Aurora in the meantime. https://www.mozilla.org/firefox/channel/#aurora
Firefox 15 *may* be the first version that supports tablets. We are trying very hard to make the 15 time frame but with time based releases we won't know until mid to late July if we have the required work done.