Hi !
For Instagram, it could be possible but I still need to figure out how I will do it exactly - but there's no technical impossibility - (as "data fetching" is very different depending on the source), but I will try to implement it as fast as I can.

For the "tag dumping" on Instagram, yes it works. It will trigger the cross-post but only for the top "Insta", so if there isn't any hashtag in it, you won't have any Steem tags (except the share2steem one).