Example at http://androidfact.com/what-happened-to-the-samsung-galaxy-s5-menu-button/

This means that apps like twicca need to test on the models noted and put out some errata note about how it changes when you have this or that Android.

--> This is also why Android is a bit of trouble. Letting the makers tinker with basics means that you can't expect apps, buttons and keys to do the same thing across machines.