Hard Reset won't save your problems.I flashed a wolf ROM 2.1 I800 to ATIV S Neo SPH-I800.
Then I hard reset from settings-about-reset your phone.
Issues such as the following has occurred.
a)settings-Cellular and SIM settings-Data connection will be forced off.
b)settings-Cellular and SIM settings-Add Internet APN, can't save APN settings.
c)Power of the phone is turned off automatically.
Hard reset or would not be?
I will cook a new MBN for you.