Native iOS Corona Enterprise plugin for UIActivity popup sharing options with text, image and url ( MMS, Airdrop, Air print, Facebook, Twitter etc.) + Instagram sharing as a custom activity.
This plugin was influenced by Cory Alders project here: https://github.com/coryalder/DMActivityInstagram
So go give him a star!
Remember: To use instagram sharing the image you share must be square and bigger than 612 px.