is there a preinstalled child lock??

[#1]

Is there a preinstalled locking syStem in the phone or should I download an app for that??

Also is there a way to hide files??

[Thommo]

You can adjust the delay from none use to lock in Settings/Display Settings

Once locked either in GB or ICS you can choose how to unlock either using a pin code or pattern lock located in Settings/Location & Security/Set up screen lock