Regarding (a), Instagram has no built-in "repost" feature. There are entire apps [1] devoted just to this purpose. [1]: http://repostapp.com/ http://repostapp.

Regarding (a), Instagram has no built-in "repost" feature. There are entire apps [1] devoted just to this purpose. [1]: http://repostapp.com/ http://repostapp.com/ (note: I have not personally used this app)