Hi,
LibreOffice is not an upgrade from Apache Open Office. I would consider it more of a side grade as they both came from the same software platform (Open Office) after a split about 3 or 4 years ago. Since then, the programs have been developed in different directions with similar/different features and are two separate programs.
Installing LO is not automatic since they are individual programs. LO would need to be downloaded and installed at your convenience. You should be able to install LibreOffice at the same time as AOO, so you can try LO to see if you like its features. No need to uninstall either program.
Since coming from the same platform, both LO and AOO have an option to let you know a new version is available for download. It’s under Tools, Options, Online Update. An option is also available to have the software downloaded automatically to the specified location. This option in AOO would have it check to see if AOO update is available; in LO, LO would check its website to see if an update is available.
There is no switch for the software to choose fresh or still. That is up to you when you go to the www.libreoffice.org to do the download. It may just get the most recent update.