1) Does Neo4jr-simple contain all the functionalities available with Neo4j?
A: Neo4jr-simple wraps up the neo4j libraries so it makes some aspects of neo4j more ruby-like but not all neo4j is enhanced. But for the entire Neo4j api is accessible from the library
2) Some RDocs for neo4jr-simple
Sorry there are not any public rdocs on the web but you can generate rdocs from the project if you pull down the source.
3) We had a look at neo4jr-social example implemented. Is it the best implementation available with neo4jr-simple or do we have any other examples?
It is meant to demonstrate the basics, I suggest looking at the wiki for neo4jr-social on github to better understand the social api. The service is meant to get you going but you will likely need to add your own extensions to it to solve your specific domain. The wiki explains how to do so.