Language & Input > AOSP Customize Icon > Advanced Settings > Custom Input Styles > Add Style > Choose Language + Layout PC > Then in next activity toggle off “Use system language” and make sure your language version of “English (PC)” is on!
source - http://nexus7.wonderhowto.com/how-to/enable-hidden-number-row-google-keyboard-your-android-0158994/
references : Install LG G3 Keyboard on Any Rooted Android! - http://highonandroid.com/android-apps/how-to-install-lg-g3-keyboard-on-any-rooted-android/ http://www.guidingtech.com/33829/add-extra-row-android-keyboard/
Android warns you about keyboard apps potentially recording everything you type, including passwords, before enabling a third party keyboard.
origin - http://www.pipiscrew.com/?p=2554 android-enable-number-row-on-keyboard