How to share only a particular link in a node using social media,instead of complete node?
If you're open to using an alternative module (instead of the Social Media module), you can get this to work for at least Facebook and Twitter by using the Rules module instead, combined with these modules:


Facebook rules (for Facebook, of course ...).
Twitter (for Twitter, of course ...).


For (way) more details on that, refer to my answer to "How to post the node link in social networking if node is published?", which also explains what the options are (that I'm aware of) for Google+.