There is a separate, similar string. You have to find a website that allows you to log in to your google account without high security. Most use plex tv site. I just learned this this week and tried it and it works. Now I am logged into any google account related website and tesla app. (Log into google from plex tv site in web browser, then go to any other site after that.)
As for adding apps not sure. Have not gotten that far beyond the 4 apps as I just got my MCU upgrade and enjoying all the items that did not or barely worked with MCU1.
Hope that helps.