1. Yep, fully functional. Everything up and running (I didn't encounter any problems)
Battery life seems worse than stock lg rom, uses a lot of battery when display on and almost nothing when it's off.
2. Make an NANDROID backup using TWRP, you can restore to it later
3. Yes, you can configure root access in the developer options. After selecting "Apps + ADB" Superuser will appear.
P.S. Keep in mind tham I am not the developer, just someone who uses this ROM as a daily driver, the developer might give you a different answer