Does all Rails 2.3.8 projects are compatible with Rails 3.0.1 and vice versa or both must be different?
If they are different means not compatible then is there any tool available which can help me convert a project made in 3.0.1 into 2.3.8 or have to do it manually?
Rails 3.0 is not backward compatible with Rails 2.3.x. Likewise, in order to upgrade a Rails 2.3 project to Rails 3.0 you might need to apply some changes.
Generally speaking, Rails 3.0 is a major version upgrade and contains several new features. You cannot simply change the underlying framework version because the two releases have several differences.
The rails_upgrade Gem can help you upgrading your Rails 2.3 project to Rails 3. I also wrote an article about making your Rails 2.3 project more Rails 3 oriented in order to have an easier transition.
