Problem explanation: Not able to connect to RDS-MYSQL instance from another EC2 instance. The other instance is an Amazon-Unix.
listed below are the things tried.
Do you mean Amazon RDS instance and you have MySQL DB installed on it. If that's what you are asking, you don't have access to instance level in AWS RDS, only DB level access is permitted. The instance is maintained by AWS, so that you can focus on the DB side.