Should I remove Rstudio version 3.4 before installing the new version 3.5 on Ubuntu 18.04

I have a new machine operated by Ubuntu 18.04. I installed RStudio v.3.4, but I can not install other R packages essential to my work basically Phyloseq since some of the dependencies are not available for V3.4. So, I need to upgrade to v3.5, but I am not sure if I have to remove v3.4 before proceeding or the 2 versions could be installed independently on the same machine.

One more thing, I ran this command

sudo add-apt-repository "deb https://cloud.r-project.org/bin/linux/ubuntu bionic-cran35/"

and at the end, I got this error message

W: GPG error: https://cloud.r-project.org/bin/linux/ubuntu bionic-cran35/ InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 51716619E084DAB9
E: The repository 'https://cloud.r-project.org/bin/linux/ubuntu bionic-cran35/ InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Any suggestions please?