backup data (Kies 3), wipe data & factory reset, apply Kit Kat 4.4.4 for XEF (last issued in jan 2015) with Odin, then again wipe data & factory reset, open phone, go to settings
> about phone
> check updates —
voila, instantly starts downloading OTA of about 849 Mb (be sure you have about 60 % battery minimum), after instal and initial settings do restore initial data (from Kies)-- everything smooth, perfect!