To upgrade to lollipop is quite straight forward. After successfully installing Vcom drivers next download and extract Smart Phone flash tools (latest version) . also download and extract the lollipop Rom .
Open flash_tool.exe a prompt dialog with display alerting you that there is no scatter file, click OK
Select scatter loading file>>> next navigate to the location of the extracted Rom open and then select the Android Scatter file it will be the only file there.
Goto option >>> connection >>> High-speed.
Select Firmware Upgrade from the drop down option and click download.
Now connect your switched off Jiayu S3 via USB cable. Wait for the process to complete you’ll see OK
Backup you phone data and maybe even create a Nandroid backup in case you decide to revert back to KitKat ( I wonder who would)
Link to Jiayu S3 5.1 : https://docs.google.com/file/d/0B1ZCUZBU0lhXY01GMlJNZnpuY1E/edit
VCOM .zip – https://www.dropbox.com/s/53zvuti4lo8f72j/VCOM%20drivers.zip?dl=0
Recovery TWRP: https://mega.co.nz/#!2sRUTI5L!4XTPjt7RBEiw8R5aKfiG8HvuiRkT7O8Q29q3kcCxP8U
Gapps : link down, use the one @dljbd1 dropped
Update SU : http://download.chainfire.eu/supersu