This design was designing based on a Feature phone.
For the touch type home button,
it appears in the menu bar after you open the app.
doesn’t show a home button on home screen.

Motive : Firefox OS 2.0 + Feature Phone Version (youtu.be/JIiIjjIsuzc)
Font : Fira Sans, Gidole
Tool : sK1 2.0 RC2.1
File : https://www.dropbox.com/s/9yuo2uqgho7s7vn/Firefox%20OS%2C%20Gaia%20UI%20%28Flimwer%20Remix%29.sk2?dl=0