Due to the power outage during the cold december month my live stock is dead since then. My question is should I redo the whole tank cycle ??? or should I do a massive water change or what ?
Assuming that the deaths were caused by low temps, how long was the tank without heat? Could some of the life on the rocks have survived? Has the tank been running since december?
Sorry for your loss. I know it's not much help now, but a power inverter that plugs into your car's cigarette lighter or hooks to a DC car battery via alligator clamps can make for cheap, basic life support in a power outage (if you can't use a generator in your situation, which would be my first choice).
What have you done to your tank since the crash? Anything? Nothing?
Sorry for your loss, but IMO/E I would have been pulling my rock at the time of crash and done some major cycling, water changes, i.e. damage control. That way by now your tank would be well on it's way to recovery and would be through the algae blooms.
If your water parameters are fine and you aren't experiencing massive algae blooms I would reseed the tank with a few fresh pieces of live rock and treat your system like a new tank.