as i know theres nothing you can do because you are on 4.31.
the cfw you are about to install (e3 or rogero 4.3 v2.03) is 4.3.
3.56-3.6 are hackable but not downgradable, sort of if we speak in terms.
remember it is used a patch in order to let you install 4.3cfw.
you had no reasen to update to 4.31 since it was not mandatory....