Default TELSDA T6618 there is option to install new rom on it ?

Hi there.
Friend give me a phone that he bought on ebay. TELSDA T6618
On it running android 4.3.1 it look's a bit wierd so i want to try install on it fresh 4.4 or any custom rom.
I was installing android last time some time ago so i;m not sure what i should do or check before try to do it.
I'm don't know what bootloader there are and what i need to install other ver. of android on it.
any suggestion what should i do ?