Default pls HELP...Sky Vega A810K

i want to install custom rom of this phone because of sms limit
but it cannot i've already root the phone but cannot insta custom ron
coz when i go to recovery mode to have sdcard update...
the sd card update was not there as and option
recovery only contain...

reboot system now
apply update from adb
wipe data/factory reset
wipe cache partition
enable ums
wipe internal sd partition
initialize sd partition
check rooting information

that all
android recovery version is <3a>
i'm trying update many times through abd but cannot

firmware version 4.2.1
kernel version 3.4.0 perf

i ve try to flash recovery like recovery version 5.8.2.0
6..1.0
but i never try to flask kernel coz i don't know
anybody can hel me please flashing this in custom firmware
thanks in advance