Downgrade from Sonoma to Monterey

Hi all!

i have a MacBook Pro 2016 and i am on Sonoma with OCLP and I want to downgrade to Monterey because battery drain but I have a couple questions

1. I tried downgrading today but it gave me preflight error 21, I didn't format the drive. if I erase it does that error disappear?
2. how is Ventura on the mcb 2016? does it drain battery fast?
3. What is the correct steps to downgrade from Sonoma to Monterey?
4. can I use backup using Time Machine on Sonoma and use it after on Monterey or Ventura?

I thank you all for the effort and reactions.