If you already got your claim backdated to December can you get it backdated further to March of 2020?

I found a way to solve reaching California unemployment representatives, watch this: https://www.youtube.com/watch?v=ayU0shkznmk

Only if you filed before dec 27 2020

To all those having trouble reaching a human at California Unemployment. I just ran across this video that gave me a shortcut to reach a human. Hope it helps! https://youtu.be/Ize0EkN4HDI