Download Android 4.4.2 KitKat ROM for JIAYU S3 smartphone from here or here. Download another Jiayu firmware from here.
Archive name: MP_mt6752_h560_s3_jyt_cc_kk_lte_5m-cs_tphone_20150117
-172407PC
Archive file size: 576 MB
Model: JIAYU S3 smartphone
Support: Mediatek MT6752
Project: vanzo6752_lwt_kk
Config_version: V1.1.2