My phone have been stolen and i havent put lock on it . so how if people steal resets my phone? does the Find my mobile still works?
No, the app will be removed along with all other apps and user data. If you root the phone, it's possible to install a tracker as a system app, such that it will only be removed if the thief flashes a new ROM, but any app you install from Google Play or another app marketplace won't be able to do that.