From what you describe, it sounds like the Home and Back buttons are still there, but only intermittently responding when you touch them? If that's the case, you may want to try going to Settings > Display > Navigation Bar, and adjust the sensitivity of the buttons there. If that doesn't resolve it, you may want to try a settings reset: Settings > Backup and Reset > Reset settings
We want to make sure you are able to operate your phone as needed. Let's look in to this more. What steps have you completed so far? Are all of your other applications updated on your phone?
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