While attempting to fix a bug in my Re-Dress mod I encountered several API-related issues.Re-Dress mod
Update 07/12/21:
Fixed an issue preventing the interaction from working correctly on family members.
Neither getPerson() nor getSpecific() will return actors that are related to you. This isn't necessarily an issue itself except there's no equivalent functions for relatives specifically where you can do something like getPerson(tag) or getSpecific(id), which means that you ultimately end up having to loop through your relatives with getRelative() trying to find the one that you tagged or with the correct ID.
setActorVar(tag, -1) does not remove the tag from the actor despite what the API docs would have you believe. If you first check for the existence of a tag on an actor with getActorVar(tag) before the tag is actually set, the function returns a value of 0, indicating that tag hasn't been set. If you then set the tag to some other value, and then later set it to -1 in an attempt to remove it, when you check again with getActorVar() you'll see it now returns -1, instead of 0 which is what you'd expect if the tag had been removed. While getPerson(tag) seems to ignore tags set to -1, it seems like the correct thing to do is set the tags to 0 if you intend to loop through actors looking for the existence of the tag.
As an aside, there's also several API functions that exist which have no documentation at all, or existing ones where new parameters were added but the documentation was never updated.