This thread covers my journey with the O2 sensor heater readiness on my 2001 3.0i.
https://xoutpost.com/bmw-sav-forums/...ncomplete.html
For your specific questions,
In California, you do not need to have the EVAP readiness ready, but all others do need to be ready or N/A.
All 4 O2 sensors on these cars are 4-wire, with two of those wires for the heater.
Specific details from the thread linked above:
I had been delaying actual sensor replacement, testing heater resistances, etc. (one challenge with that is that the resistance will be different when the heater is actually heating, which the car knows about, but I do not), and finding everything good except the readiness.
Then finally replaced the downstream sensors (upstream ones were relatively new). It then took 205 miles of normal mixed driving for the readiness to be ready.
"So at some point, even after testing the 3-year old Bosch upstream sensor heaters, the original upstream ones, and the original downstream ones - all as good and self-consistent resistance values; no O2 codes - I figured it was easier to at least replace the downstream sensors, so I did with new Bosch 15109 ones, at 198,728 miles.
It was not until 198,933 (205 miles later, with a mix of city and highway driving) that the final monitor completed."