If you have a relatively new FP2 (screen) then be aware that old versions of FP OS (which you’ll need to go to first before upgrading to the latest version) will not work with the screen. Here is another way to go back if you prefer recovery over fastboot.
Very.
My battery life is great.
Here is a screenshot. Note that I use Battery Charge Limit. That’s why the battery never gets above 80%.
I have never had reboots with any OS.