To forget all existing wifi connections you can just remove the wpa_supplicant.conf file:
sudo rm -rf /etc/wpa_supplicant/wpa_supplicant.conf
or edit it if you want to remove specific network:
sudo nano /etc/wpa_supplicant/wpa_supplicant.conf
Regarding Virtual Access Point (VAP) - there has been a problem with a script recognizing RPi version in the initial release. It is already fixed in the latest system image, so you can either redownload the image and reflash the SD card or replace the script with the latest one:
wget https://github.com/rkaczorek/astroberry-server/blob/master/scripts/astroberry_vap
sudo mv astroberry_vap /usr/local/bin/astroberry_vap
If you don't see VAP it might also mean that your PC does not support wireless AC mode (default for RPi 3B+)
In such a case see the last question and answer in
FAQ
You can change all the regional settings in a regular way by entering system settings and choosing your locale.
RPi does not have a real time clock (RTC) so it get the current time from the Internet. If after a few minutes from starting the system the time and date is not updated automatically, you are probably not connected to the Internet. In such a case you can set the time manually with timedatectl. Just make sure you disable NTP before by running: sudo timedatectl set-ntp 0
Happy New Year!