SamyGO

Yup. I think it's compatible with LA too. LA means Asian version, LE is European.
Since HW are nearly same, you can use those hacks too.
But don't wait too much things. Because you are limited with your HW. Your modal number is low to support most of tools.

I advice you before starting read wiki pages and "understand" what happening.
I think you just needed to try. Report if you have success.

AFAIK you just needed to change modal number to play movies. No flashing and no cables are required. (Also C series need vga to rs232, not 3.5 jack )...
Caution, if you change modal number, you can also brick your TV. So risk is yours...

Himm. That means they removed other models from LA firmware.
And you dont needed to change / flash your firmware again. We do not put any firmwares for C series. So nothing to flash.
It looks like nothing to do...
You can search on service menu if there is a way to enable it.
But as you well know, responsibility is yours...

You are just going to brick your TV. Nothing more...
You cannot flash another firmware to your one.
For flashing new firmware you have to be sure that is compatible with your TV.
And VAL4DEUC uses ARM chip, MSX uses mstar and tdt uses tridend...
I don't know which firmware fits to your TV but you have to find exactly same firmware before you try...