yes. you can look at the Home MRAN timemachine to see what the latest package version was on cran/mran at a point in time.
yes. do your work witin rstudio projects and use renv package to record the versions used
Also, I recommend you leverage RStudio's ability to integrate with git and github to source control your projects.
https://r-bio.github.io/intro-git-rstudio/