always wipe data when downgrading. you can do that from recovery.
1. Power off the phone
2. Press [Vol. Up] + [Home] + [Power] button
3. Use [Vol. Up] and [Vol. Down] to up/down, [Home] to select
4. Choose factory reset (all data will be wiped)
5. Reboot
BAck up all ur data however u can. switch of your phone .press: menu button+lock button+volume up button until u see an android logo. from their u can restore the factory settings. User data doesnt get earased...but incase phone gets bricked....backing up is just a safety precaution.
always wipe data when downgrading. you can do that from recovery.
1. Power off the phone
2. Press [Vol. Up] + [Home] + [Power] button
3. Use [Vol. Up] and [Vol. Down] to up/down, [Home] to select
4. Choose factory reset (all data will be wiped)
5. Reboot