User story vs. Use case

Few things about the possible differences between these concepts
1) A user story is the title of one scenario, whereas a use case is the contents of multiple scenarios.
2) User story is written by customer before getting into actual conversation, where in use case is formal record of that conversation

Does OOA/D steps helps experienced developers?

In my opinion it is not mandatory to follow all OOA/D steps while individual has enough experience and knowledge on problem domain. In other words, if individual is comfortable with all architecture/design styles, patterns and principles, he/she could directly start coding.