Hi,
RStudio is an IDE that exists on top of R. The warnings are just warnings, with the exception of the grid warning, which sounds like you need to update your version of R if you want to use it.
There's a really nice, quick explanation of the difference between R and RStudio at the link below, and it also has the links to where you can download an updated version of R.
http://moderndive.com/2-getting-started.html