How does the api for vkontake, facebook and instagram work?

Question

Facebook

Good morning, We are
writing technical specifications for the site, including presence in social networks. Specify whether it is possible to perform the following actions through the api for social networks from the list to my question:
- when adding new data to the site via CMS, immediately send messages to the appropriate social media feeds "updating projects, see the link"?
- when registering through your social network account on the site, the user of the site subscribes to updates, registers in a group, receives notifications about contests and drawings, discounts, etc.?
 Thank you.