how to downgrade Andriod on TC55

i have applied image update on TC55 of andriod kitkat 4.4.3 and it seems not compatable with TC55 as Wifi not working  anyway

am trying to downgrade it to last compatable version on it and it seems when i turn power off then press the upper volume with power to downgrade the option upgrade from SD card is no longer there, so i choose from external then select the folder which have the version image update but seems it doesnt read or accept image update files here and am not sure what to do.


any ideas??.

sorry for my poor English