As per the GET help/languages docs:
Returns the list of languages supported by Twitter along with the language code supported by Twitter.
The language code may be formatted as ISO 639-1 alpha-2 (en), ISO 639-3 alpha-3 (msa), or ISO 639-1 alpha-2 combined with an ISO 3166-1 alpha-2 localization (zh-tw).
msa are what’s expected as a parameter from Twitter’s end; all codes are returned from the above endpoint, so you can combine the data from the supported languages doc and the aforementioned endpoint.
You are correct, we support all types of Portuguese.
This discussion around country codes is outside of the scope of the Ads API by the way, so if you have any further questions around this that are not specific to the Ads API it might be best to open a thread in one of the other sections of the forums.
Hopefully I have been helpful