[Q] How to Downgrade from 4.3 unofficial rom to official 4.2.1 rom topic

Hi,

I am not a techie but I had upgrade my galaxy note 2 with unofficial rom of 4.3 , I am facing following issues so want to downgrade it to official version, please give me the procedure.

CURRENT DETAILS:
ANDROID: 4.3
ROOTED: YES
MODEL: GT-N7100
BASEBAND: N7100XXEM16
BUILD NUMBER: JSS15JN7100XXUEM16

ISSUES:- 1)Battery drain
2) After call gets connected, am not able to see the screen until call is hanged up.
3) other small issues.