Face ID

If the app you are trying to add Face ID to requires it, it will request permission. If you accidentally press “don’t allow” or it doesn’t ask, go to settings > the app name > Face ID (Turn it on)(It will be green and have a smiling face within a frame).

Probably yes. You should just be able to type in to google, “does (app name) support Face ID?”. It will hopefully then say yes or no.