Yes you can install via Play Store and also directly

Android Google Play Strore

• https://play.google.com/store/apps/details?id=org.mozilla.firefox

Download from the FTP Sever and install it

• http://ftp.mozilla.org/pub/mozilla.org/mobile/releases/28.0.1/

No, this user is not talking about Firefox for android, they are talking about Firefox os on that phone.

SEE: https://developer.mozilla.org/en-US/Firefox_OS/Firefox_OS_build_prerequisites and https://developer.mozilla.org/en-US/Firefox_OS/Installing_on_a_mobile_device

Though I dont see your phone displayed on that page.

not firefox browser i am asking about firefox Operating system.

Did you see my last post?

Like Waka_Flocka_Flame said, the link provided were:
https://developer.mozilla.org/en-US/Firefox_OS/Firefox_OS_build_prerequisites and
https://developer.mozilla.org/en-US/Firefox_OS/Installing_on_a_mobile_device

These are the documents we presently have for installing Firefox OS onto another operating system.