Hi @revolve: Just make clear, you're writing to a community of R and RStudio users here, most of whom are not involved in developing either.
What you likely experienced is that when you upgrade R, you lose access to previous packages you had (like ggplot2), so you have to take steps to regain access. This can be done either by re-installing the packages, or by manually moving the packages to a new location, something I'll leave for others to advise on.
When a package you install has been built using a different version of R than your version, you may see a warning alerting you to that fact, so that you can update either R or the package as needed. This doesn't mean there's necessarily an incompatibility, although if the two versions of R are far enough apart in time, that could be the case.
I hope that helps.