Acer Liquid Z3 User Manual page 44

Note: Before performing a clean boot, ensure that your smartphone is not
locked. Press any key or tap the screen to see if the phone responds.
Warning! You should only perform a clean boot when all other options
have failed to restore your smartphone to an operational state.
Warning! This will erase all your personal information, any contacts stored
on your phone and any programs you installed.
If your phone is responding to screen input, then open Settings from the Application
menu. Tap Backup & reset > Factory data reset > Reset phone and then Erase
everything to format your phone.
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