Ruby is NOT a framework, it's a programming language. Rails (as in Ruby on Rails) is a framework. There is a major difference. Regarding the styling of components, just like PHP or ASP, Ruby is not involved in the stylistic stuff of what ends up in the clients web browser, that's the job of CSS.
It's about as secure as any other language, but with all things, you need to be sensible in how you use and implement it.
No, if the host supports Ruby, you can deploy Ruby code, just like if the host supports PHP, you can deploy PHP scripts.