Reset Galaxy Young: Charge your phone fully.
OR Press Volume UP + MIDDLE HOME key + POWER on.
(or Press Volume UP + MENU + POWER on.)
Select wipe data / Factory reset and confirm. All data will be lost!

If your device has fatal errors or hang-ups, or freezes, you may need to reset the device to regain functionality.
Reset the device: press and hold POWER/Lock button for 8-10 seconds, then release it.
Settings > Location and security > Clear storage: Erase the credential contents from the device and reset the password.
Samsung Galaxy Y Plus S5303 hard reset Vodafone Galaxy Y Plus

Your device freezes or has fatal errors

Perform a factory data reset. In Idle mode, open the application list and select:
If your device is frozen and unresponsive, press and hold for 8-10 seconds. The device will reboot automatically.
If this does not solve the problem, perform a factory data reset. In Idle mode, open the application list and select
Settings > Back up and reset > Factory data reset > Reset device > Delete all.
Reset your settings to the factory default values and delete all your data.
or
Use this method to hard reset your Samsung Galaxy Y Plus GT-S5303: Enter *2767*3855#. Warning! All your data including contacts, messages etc. will be lost! Copy all your necessary data/Contacts/Messages etc. to SIM or make backup to your PC before full reset! Take out SIM card before full reset.
When disposing of your device, back up all data and then reset your device to prevent misuse of your personal information.