my s4 is no variant.If I were you, I would:
- Do a complete reflash with stock Odin
- Install TWRP recovery (with the all-in-one tool pertaining to your S4 variant)
- Do a full factory reset/wipe. (NOT FORMAT)
- Flash this rom and the mods of your choice
moreover don't have warranty & had fully fresh rom.
Now please advise the full process & what i have to do. More over is that also a pure andriod version from Google which jut released now.