| As a former WhatsApp engineer, I don't think WhatsApp even has any mechanism to do such a thing. It's probably an unintended artifact of its infrastructure that the Iranian government has exploited, and knowing the WhatsApp team, they are probably already working on a fix.
(As much as I dislike Meta —) applying foreign laws to foreign users isn't "dealing" with the Iranian government. "Dealing" in the legal sense generally requires a two-way exchange. If Iran unidirectionally imposes a regulation, that's not a deal; Meta has made no decision to enter into it.
(Reference/entry point for legal aspects about this: contracts are also invalid if they're purely unidirectional. If I remember correctly there's a LegalEagle YT video about this, but you can probably dig this up elsewhere too.)
Possibly. Sanctions law is a hot mess of sometimes contradictory exceptions. In this case, the exceptions regarding "informational materials" may apply.
