Is obsolete to study older versions of Ruby and RoR?

I want to study Ruby and RoR for some things I'll have to make, but almost every book, videos or any kind of source I find is outated, where the most current book I could find is one of the version 2.1 (latest stable version of Ruby is 2.2.0), and in the case of Rails I only find books about RoR 3.x or at most 4.0 (latest stable version is 4.2.0).

Then I wondered if there are many changes in Ruby and RoR, for example, if I find a good book about Ruby 1.9, should I read it?, are there many changes?, the same in the case of Rails, if I find videos of Rails 3.x, should I see them?.